How to comment on posts or other comments

The Fediverse uses two different ways of combining posts and comments

Our way (used by Streams, Forte, Hubzilla, and a few other types of Fediverse software):

A conversation is like a "container". The person who makes the first post owns that container, and controls what is allowed in it. (This is similar to how Facebook works.) The original poster decides who can see the conversation, and who can comment.

If you comment on a conversation container, it's something like selecting "Reply to all" in an e-mail. Your comment is first delivered to the original poster, and (if accepted) is then forwarded to everyone else who is allowed to participate in the conversation.

Their way (used by Mastodon and most other Fediverse software):

Each post, and each comment, can be addressed to a completely different audience. (This is similar to how X/Twitter works.) There is no single canonical version of an entire conversation. There is no complete list of all the participants, so "Reply to all" is unsupported.

Instead, there are several incomplete collections of related comments, which are delivered to some people. Anyone can comment, and the commenter chooses who will receive the comment (although other people might also receive a copy).

Commenting on posts created "our way"

You can recognize our "conversation container" posts by the briefcase icon, just to the left of the original poster's name. If you have permission to comment, you will see a comment box at the bottom of the conversation, marked with a "Reply to conversation" arrow. Click/tap in this box to add your comment to the conversation.

Conversations can be "threaded": you can comment on another comment, and your new comment will be inserted into the conversation in the correct place. Look for a "Reply" arrow beneath the comment that you want to reply to.

Commenting on posts created "their way"

If there is no briefcase icon, you're looking at a post, and possibly some comments, generated by Mastodon or other software that doesn't support conversation containers. Most likely, you will not see all the comments. And there is no "Reply to conversation" box.

Click/tap the "Reply" arrow beneath the post or comment that you want to reply to. By default, your comment will be delivered to the person you're replying to, and to anybody they were replying to, and to your own connections.

If you want additional people to see your comment, you'll need to manually "mention" them by name. Type an "@" symbol, followed by the first few characters of a person's name or Fediverse address. A dropdown list should let you select the right recipient. Add as many names as you want, separated by a space character.

Advanced: How to comment on something that isn't in your stream

Suppose you find a post or comment on a different Fediverse instance from your own, and you want to reply. There are two ways to do this:

The easy way — Go to the other instance and write your comment:

The other Fediverse instance might recognize you, and automatically log you in, even though you don't have an account there. We call this "OpenWebAuth" or "Magic Auth". Make sure you're logged in on your home instance, then visit the other instance and see whether you can comment. (This generally works only on Streams, Forte, and Hubzilla instances, and sometimes fails for technical reasons.)

The normal way — Import the item to your own instance and comment from there:

You'll need to tell your home instance where to find the item. On the other Fediverse instance, find the URL (the web address link) of the exact post or comment that interests you. Usually this will be in the date/time stamp of that item. Copy that URL.

Then, on your own instance, click/tap the Search icon in the top navbar, or select Search from the menu. Paste the URL in the box, and search. Your instance should find and import the item. Now you can comment in the usual way.