I missed it.
Is it sorted by rshares instead of MVests?

Votes are sorted by timestamp of casting as to distinguish between the downvote and the flag part of the negative vote. This is an important distinction as the downvote part will only cut into the payout of the post in question while any vote that would bring the payout below zero will end up cutting into the reputation of the author of the original blog post or comment.

?

A downvote cuts into reputation if the voter's reputation is higher than the votee's
The only differences between flagging above zero and flagging below zero AFAIK is that below zero only reputation is affected and I am lamost sure that it creates a deeper hole of negative rewards which translate to 0 rewards by payout time.