I mean ... flagging a comment as an idea is a good starting place ... but maybe it's more subte ... thinking here:
- someone comments
- someone else notices the comment and sees it as an idea or a starting place for and idea, or some inspiration, etc.
- they flip the comment over (or something) and are presented with a text box that lets them elaborate a bit, another box to enter "pitchees", and a "pitch" button
- if the pitched comment + elaboration blurb get some traction (x amount of replies) it is converted into an idea