> Probably a bunch of them have opened my submission history in a new tab by now to mass downvote

Two things work against that. First, it requires a sufficiently high karma to downvote something. Not that threshold is that high, but it takes more than a casual person's activity to get quickly.

Secondly, you can't downvote something older than 24 hours. So nothing you said yesterday would be down-voteable.

You can also vouch for something that has been marked dead if you believe that something written contributes. If one believes that it is a minority of highly active users that prune undesirable opinions, then vouching for those would make those comments viewable again.

That said, make sure that vouching for things isn't based on a desire to be contrary. https://news.ycombinator.com/item?id=10298512