What is the difference between a Comment Section and a feed?

Twitter has the same

Why should we have the Comment Box at the top or bottom?

Threads and Bluesky had incredible growth just by replicating the Twitter Feed. Should we do the same thing?

WhatsApp

Primary action: Sending a message.

The comment box (message input) is at the bottom because that’s where your thumbs naturally rest on a phone, making it faster and more ergonomic for continuous conversation.

The flow is read → type → send → read again, all in a single continuous vertical scroll anchored at the bottom.

Facebook (posts & comments)

Primary action: Consuming content first.

The comment box is often at the top of the comment list (under the post) so you can respond before scrolling through other comments, or after reading the post headline/content.

The flow is read the post → decide to comment → optionally scroll through other comments. The positioning encourages engagement without forcing you to see every other comment first.

Why Reddit puts the comment box at the top of the thread

Primary action: Reading the post and its context first.

Reddit’s design assumes you want to see the original post before writing your own comment.

The comment input is right under the post (above all other comments) so you can reply immediately without scrolling past potentially hundreds of comments.

This also subtly encourages top-level comments, which help start new discussion branches, rather than burying new contributions deep in the thread.

Difference from Facebook

Facebook threads are usually shorter and more conversational, so the “comment at top” is about quick engagement.

Reddit threads can be huge, so the “comment at top” is also a navigation shortcut for people who just want to contribute without reading it all.

Twitter

Hypothesis

Async versus Sync

Community Size

0-100

100-1000

1000-1000