Market cap remains the same only if demand does not increase. If payouts are made to (sufficiently) value-adding posts then it should increase demand more than enough to offset the dilutive effect of more coins. Voting for burnpost is expressing a view that the weighted average of other posts is not value adding.

I was mostly agreeing with you BTW. I do personally vote for burnpost so my opinion is that fewer coins -> higher price under current conditions, but I just wanted to acknowledge this is opinion not objective fact.