My inital thought:
To my mind, users commenting on your answer with positive suggestions do so because they essentially agree with it, but rather than write a new answer with their minor tweak (which would be seen as a rude attempt to jump in and steal rep) they instead are helping you to make your answer exemplary.
To address each of your points:
If many comments have to be included, mentioning the source of each added piece of information will hurt answer's brevity and clarity.
- Moreover, how should this be done? Should I only use the username or the username linked to their profile page or write something like This piece of information was posted by ... as a comment?
Not sure if there's an offical line on this, but here's my personal thoughts:
I don't think it hurts brevity or clarity to just say
"As per user_name's comment ...", and in the case of comments I have sometimes linked to the profile page (after all - their username could change), if I remember to. You can also use
"... with thanks to user_name's comment" if a prefix to the information doesn't work well (for example, I think it's neater to postfix the notice if it sits within a list).
I've even used variants of
"As per user_name's [answer] ...", and hyperlinked to another answer on the same question, if another user has beat me to something I wanted to say, but while my answer has wider scope I still need to say that for my answer to be correct.
The same information will appear twice - in the answer and in the comments - unless the original author removes the comment.
I don't see this as a real problem, comments are pretty low-profile and don't really get in the way that much even if they contain duplicate information.
And, it's best to place the details in the answer even if it does duplicate, because comments often get rolled up so some are not displayed - potentially hiding the information from unwary readers.
Sometimes I know that the comment contains useful information, but I don't understand it well enough to write about it myself.
This is a tricky one, and is a very good reason to not update your own post.
Afraid I don't really have an answer here, possibly ask the person posting the comment to explain, edit or write a seperate answer and hope they do?
Why don't people want to edit answers posted by others?
I recommend reading The Great Edit Wars blog post and What is the etiquette for modifying posts?
From these the mains points for good editing practice are given as:
- Fix grammatical or spelling errors.
- Clarify meaning without changing it.
- Correct minor mistakes.
- Add related resources or links.
- Always respect the original author.
Adding any extra information to a post (a question or answer) will in most cases change it's meaning and so is frowned upon.
When a user with edit powers is posting a comment to an answer, is a message displayed to remind about possibility to edit the answer?