Well, serial voting can be reversed, and votes imported from SE can be changed.
Votes imported from SE are only changed with accordance to this thread: Not-very-high quality imported posts queue.
There has not been a single case of serial voting in the past.
Be assured, that any use of these tools will be recorded, openly, and not secretly done (in fact, I had initially forgotten about the existence of these plugins, and had was about to post a one-word answer "No"). Actually, we don't even check voter identities.