Comments are piece of text left by users under a post.
Some special actions can be performed on them.
Formatting a comment
When writing a comment, you can use DText to format it, e.g. by making it bold.
Read the linked page for more informations.
Rating a comment
Comments can be given a positive or a negative vote.
Normally, comments with a rating of -1 or less are hidden, but this threshold can be changed in the account settings.
You can search the comments like you'd search posts, except that instead of searching for tags, you search for words used in the comment.
Follow the rules
Read this page before commenting: howto:comment.