diff --git a/public/src/client/topic/posts.js b/public/src/client/topic/posts.js
index b84953e915..1301e7289a 100644
--- a/public/src/client/topic/posts.js
+++ b/public/src/client/topic/posts.js
@@ -183,7 +183,7 @@ define('forum/topic/posts', [
 			}
 
 			data.posts = data.posts.filter(function (post) {
-				return $('[component="post"][data-pid="' + post.pid + '"]').length === 0;
+				return post.index === -1 || $('[component="post"][data-pid="' + post.pid + '"]').length === 0;
 			});
 		}
 
@@ -206,9 +206,11 @@ define('forum/topic/posts', [
 
 		app.parseAndTranslate('topic', 'posts', Object.assign({}, ajaxify.data, data), function (html) {
 			html = html.filter(function () {
-				const pid = $(this).attr('data-pid');
-				const isPost = $(this).is('[component="post"]');
-				return !isPost || (pid && $('[component="post"][data-pid="' + pid + '"]').length === 0);
+				const $this = $(this);
+				const pid = $this.attr('data-pid');
+				const index = parseInt($this.attr('data-index'), 10);
+				const isPost = $this.is('[component="post"]');
+				return !isPost || index === -1 || (pid && $('[component="post"][data-pid="' + pid + '"]').length === 0);
 			});
 
 			if (after) {
diff --git a/src/socket.io/topics/infinitescroll.js b/src/socket.io/topics/infinitescroll.js
index c20730229f..506a87b6f7 100644
--- a/src/socket.io/topics/infinitescroll.js
+++ b/src/socket.io/topics/infinitescroll.js
@@ -16,7 +16,7 @@ module.exports = function (SocketTopics) {
 
 		const [userPrivileges, topicData] = await Promise.all([
 			privileges.topics.get(data.tid, socket.uid),
-			topics.getTopicFields(data.tid, ['postcount', 'deleted', 'scheduled', 'uid']),
+			topics.getTopicData(data.tid),
 		]);
 
 		if (!userPrivileges['topics:read'] || !privileges.topics.canViewDeletedScheduled(topicData, userPrivileges)) {
@@ -32,28 +32,22 @@ module.exports = function (SocketTopics) {
 			parseInt(data.count, 10) || meta.config.postsPerPage || 20
 		));
 
-		if (data.direction === -1) {
-			start -= (infScrollPostsPerPage + 1);
+		if (data.direction === 1) {
+			start += 1;
+		} else if (data.direction === -1) {
+			start -= infScrollPostsPerPage;
 		}
 
 		let stop = start + infScrollPostsPerPage - 1;
 
 		start = Math.max(0, start);
 		stop = Math.max(0, stop);
-
-		const [mainPost, posts, postSharing] = await Promise.all([
-			start > 0 ? null : topics.getMainPost(data.tid, socket.uid),
-			topics.getTopicPosts(data.tid, set, start, stop, socket.uid, reverse),
+		const [posts, postSharing] = await Promise.all([
+			topics.getTopicPosts(topicData, set, start, stop, socket.uid, reverse),
 			social.getActivePostSharing(),
 		]);
 
-		if (mainPost) {
-			topicData.mainPost = mainPost;
-			topicData.posts = [mainPost].concat(posts);
-		} else {
-			topicData.posts = posts;
-		}
-
+		topicData.posts = posts;
 		topicData.privileges = userPrivileges;
 		topicData.postSharing = postSharing;
 		topicData['reputation:disabled'] = meta.config['reputation:disabled'] === 1;
diff --git a/src/topics/index.js b/src/topics/index.js
index 67614927ae..9584b8d7cf 100644
--- a/src/topics/index.js
+++ b/src/topics/index.js
@@ -168,7 +168,7 @@ Topics.getTopicWithPosts = async function (topicData, set, uid, start, stop, rev
 		thumbs,
 		events,
 	] = await Promise.all([
-		getMainPostAndReplies(topicData, set, uid, start, stop, reverse),
+		Topics.getTopicPosts(topicData, set, start, stop, uid, reverse),
 		categories.getCategoryData(topicData.cid),
 		categories.getTagWhitelist([topicData.cid]),
 		plugins.hooks.fire('filter:topic.thread_tools', { topic: topicData, uid: uid, tools: [] }),
@@ -211,58 +211,6 @@ Topics.getTopicWithPosts = async function (topicData, set, uid, start, stop, rev
 	return result.topic;
 };
 
-async function getMainPostAndReplies(topic, set, uid, start, stop, reverse) {
-	let repliesStart = start;
-	let repliesStop = stop;
-	if (stop > 0) {
-		repliesStop -= 1;
-		if (start > 0) {
-			repliesStart -= 1;
-		}
-	}
-	const pids = await posts.getPidsFromSet(set, repliesStart, repliesStop, reverse);
-	if (!pids.length && !topic.mainPid) {
-		return [];
-	}
-
-	if (topic.mainPid && start === 0) {
-		pids.unshift(topic.mainPid);
-	}
-	const postData = await posts.getPostsByPids(pids, uid);
-	if (!postData.length) {
-		return [];
-	}
-	let replies = postData;
-	if (topic.mainPid && start === 0) {
-		postData[0].index = 0;
-		replies = postData.slice(1);
-	}
-
-	Topics.calculatePostIndices(replies, repliesStart);
-
-	await Topics.addNextPostTimestamp(postData, set, reverse);
-	return await Topics.addPostData(postData, uid);
-}
-
-Topics.addNextPostTimestamp = async function (postData, set, reverse) {
-	if (!postData.length) {
-		return;
-	}
-	postData.forEach((p, index) => {
-		if (p && postData[index + 1]) {
-			p.nextPostTimestamp = postData[index + 1].timestamp;
-		}
-	});
-	const lastPost = postData[postData.length - 1];
-	if (lastPost) {
-		lastPost.nextPostTimestamp = Date.now();
-		if (lastPost.index) {
-			const data = await db[reverse ? 'getSortedSetRevRangeWithScores' : 'getSortedSetRangeWithScores'](set, lastPost.index, lastPost.index);
-			lastPost.nextPostTimestamp = data.length ? data[0].score : lastPost.nextPostTimestamp;
-		}
-	}
-};
-
 async function getDeleter(topicData) {
 	if (!parseInt(topicData.deleterUid, 10)) {
 		return null;
diff --git a/src/topics/posts.js b/src/topics/posts.js
index dc947c6e67..5185ce4066 100644
--- a/src/topics/posts.js
+++ b/src/topics/posts.js
@@ -4,6 +4,7 @@
 const _ = require('lodash');
 const validator = require('validator');
 const nconf = require('nconf');
+const winston = require('winston');
 
 const db = require('../database');
 const user = require('../user');
@@ -20,12 +21,67 @@ module.exports = function (Topics) {
 		await Topics.addPostToTopic(postData.tid, postData);
 	};
 
-	Topics.getTopicPosts = async function (tid, set, start, stop, uid, reverse) {
-		const postData = await posts.getPostsFromSet(set, start, stop, uid, reverse);
-		Topics.calculatePostIndices(postData, start);
+	Topics.getTopicPosts = async function (topicOrTid, set, start, stop, uid, reverse) {
+		if (topicOrTid && typeof topicOrTid !== 'object') {
+			// TODO: remove in 1.19.0
+			winston.warn('[deprecated] Topics.getTopicPosts(tid, ...) usage is deprecated, pass a topic object as first argument!');
+			topicOrTid = await Topics.getTopicData(topicOrTid);
+		}
+
+		let repliesStart = start;
+		let repliesStop = stop;
+		if (stop > 0) {
+			repliesStop -= 1;
+			if (start > 0) {
+				repliesStart -= 1;
+			}
+		}
+		const pids = await posts.getPidsFromSet(set, repliesStart, repliesStop, reverse);
+		if (!pids.length && !topicOrTid.mainPid) {
+			return [];
+		}
+
+		if (topicOrTid.mainPid && start === 0) {
+			pids.unshift(topicOrTid.mainPid);
+		}
+		const postData = await posts.getPostsByPids(pids, uid);
+		if (!postData.length) {
+			return [];
+		}
+		let replies = postData;
+		if (topicOrTid.mainPid && start === 0) {
+			postData[0].index = 0;
+			replies = postData.slice(1);
+		}
+
+		Topics.calculatePostIndices(replies, repliesStart);
 
 		await Topics.addNextPostTimestamp(postData, set, reverse);
-		return await Topics.addPostData(postData, uid);
+		const result = await plugins.hooks.fire('filter:topic.getPosts', {
+			topic: topicOrTid,
+			uid: uid,
+			posts: await Topics.addPostData(postData, uid),
+		});
+		return result.posts;
+	};
+
+	Topics.addNextPostTimestamp = async function (postData, set, reverse) {
+		if (!postData.length) {
+			return;
+		}
+		postData.forEach((p, index) => {
+			if (p && postData[index + 1]) {
+				p.nextPostTimestamp = postData[index + 1].timestamp;
+			}
+		});
+		const lastPost = postData[postData.length - 1];
+		if (lastPost) {
+			lastPost.nextPostTimestamp = Date.now();
+			if (lastPost.index) {
+				const data = await db[reverse ? 'getSortedSetRevRangeWithScores' : 'getSortedSetRangeWithScores'](set, lastPost.index, lastPost.index);
+				lastPost.nextPostTimestamp = data.length ? data[0].score : lastPost.nextPostTimestamp;
+			}
+		}
 	};
 
 	Topics.addPostData = async function (postData, uid) {