I have a question about my Mathematics Stack Exchange post: Meaning of “modulo the identity matrix”

1. Sorry if this is the wrong place for these Qs; I'm new to math.stackexchange and I don't know where to ask these Qs. If this is the wrong place, where should I ask Qs like these?
2. I posted a Q about 𝑃𝑆𝐿(2,𝑅) Oct. 22. Three comments and 1 answer were posted in response. How do I respond to a specific comment and how do I respond to an answer?
3. I got the idea that I should respond to an answer by editing my original Q. Is that right?
4. If I edit my original Q, say, a month or two later, how will anyone see my edits so they might respond to my edits? Thanks.
• You can respond to a comment by writing another comment. If you want to address only one of the commenters, you can put in the string @username in the comment. Like @Jyrki would alert me, @lulu would alert Lulu (under your question, but not here, because Lulu has not commented here). Sometimes this is superfluous (when addressing the sole commenter, or when commenting under an answer). This mechanism (sometimes called @-ping) shows in the toolbar as a red number next to the INBOX icon. Nov 15, 2021 at 18:56
• You are free to edit your answer. An edit a month later will "bump" it to the front page, and the interested users will see that an edit has been made. Don't overdo "bumping" though. It pushes questions from others off the front page, and at some point frequent bumping will be seen as an attempt to hog the front page. Nov 15, 2021 at 19:00
• See this for more details about the at-ping. It gives more links to stuff describing the behavior of the software. Read sparingly. Otherwise you will be overwhelmed :-) Nov 15, 2021 at 19:10
• To respond to an answer, by another user, you can comment below the answerer's post. All comments below an answer inform the one who answered. Just so you know, no matter what a user's reputation total, an asker can always comment below their question, and comment below an answer. Hope this all helps! Nov 15, 2021 at 21:38
• But note that a user needs to have a certain number of points to post comments (other than at the user's own question), so you might not be able to post a comment in reply to a comment (elsewhere). Also, if you edit a question, it goes into the edit history, so other users coming along can see exactly what you've done (if they've a mind to). Nov 16, 2021 at 6:20
• Thanks to everyone. Nov 26, 2021 at 17:50
• I have a few more meta Qs. 1) What do the little gray numbers to the left of comments mean? How does the numbering system work? 2) To the left of answers there are boxes containing something like a 7 above the word "answers." Some boxes are colored orange, some have no color (white). What's the difference? 3) Things like tiny triangles or tiny circles are sometimes colored orange, yellow, gray, or white. What's the meaning of these colors? 4) Most importantly, is there somewhere I can read about all such things? Thanks. Nov 26, 2021 at 19:28