Where should I post a lengthy follow-up to an answer to my question? My comment ran to too many characters. Should I answer my own question, although it's really a response to one particular answer?
You shouldn't post an answer in reply to an existing answer, unless it somehow constitutes an answer to the question itself. Sometimes this type of material is best edited into the question: I tried
[answer](url) and this is what happened..., but sometimes it doesn't really fit there.
You can post multiple comments if you run out of characters. Ideally, comments will lead to improvement of the answer and can later be removed.
You can also invite the user to chat if they have enough reputation. Chat allows formatting of multi-line code, unlike comments.
Occasionally, if I want to explain or demonstrate something that won't be easy to read in comments, like show a command and its output, I use https://paste.ubuntu.com/ and post the link in a comment.