and now there will be a 25% free downvoting feature which means people will downvote for any stupid reason they can think of downvoting for

Downvotes always just shift rewards from one place to others so they have no effect on the total rewards. If you manage to get fewer than your share of downvotes, even if you still get some, your share of the pool will go up. The idea is that obvious reward milkers especially the larger ones, should be clear downvote magnets, so for most users getting fewer downvotes than they are should not be difficult (unless you are a reward milker).

How effectively downvotes will be used (or even if they will be used) remains to be seen.