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You can give credit to a comment (like "Dan's comment helped me"), but if someone has posted an answer in the comments, I will usually encourage them to post an answer, but after some time, I will post it as an answer myself and put a note like:
This answer came from a comment by Dan.
Because we really need to break the habit of posting answers in ...
It doesn't really matter how you embed the @mention into your comment.
You can even put it somewhere in the middle of your sentence or at the end too, although at the beginning makes it easier to see who you are addressing at once glance, if multiple people are discussing.
Just remember that you can only mention one user per comment, and that the user has ...