[ionfish]

Flags are a binary mechanism just like voting, and as such are vulnerable to precisely the same epistemic problems. As you say, comments offer a way of demonstrating expertise, not merely asserting it.

For this reason someone interested in a disputed topic such as this will either have to read the comments, in the hope of discovering the main lines of argument and improving the likelihood that the picture they form is correct, or suspend their judgement until such a time as better evidence (in this case, peer review of the claimed proof) is available.