It should be possible to report comments as unsourced

[haydenbetts]

Not all premises require sources, but many do, and they remain unsourced. Often it clogs up an argument thread to continually respond to premises with "but" premises says "where is the source for that?"

Proposed solution:
Make it possible to report that "this premise needs a source." This flag would function as a downvote, lowering a premise's score by one for every time it is so flagged.