Reporting them at the very least sends a message to the mods of the community the reported post/comment was on. Not sure about how/when it goes to instance admins, though. Which is where they really need to be reported to. Mods can block them from their community, but a spammer (human or bot) generally affects the entire server so it needs to go all the way to the top.
Blocking them also works to at least reduce the bots’ effectiveness. If everyone blocks it, it isn’t doing anything but wasting bandwidth, and if it’s not having the desired effect whoever deployed it might give up.
PugJesus
livus