Have an optional text box (like all .self posts have) for link posts too

I think the ability to add an explanation of a link, or a justification for posting it in a text box at the top of the comments section would be helpful.

Some posts need clarification, or sometimes the OP has relevant information that makes a post more meaningful. The OP can put this in the comments, but it will get lost if there are more than 50 comments.