Well, if the bot is plainly incorrect, as it is in the example above from the post by @carface, it's plainly annoying and worse than pointless. People using 'then' in place of 'than' is one of my personal pet hates, but in this instance, the bot is wrong. The sentence in question is a bit of a mess, but changing the 'then' to a 'than' doesn't rectify the situation...
If, however, its suggested corrections WERE actually correct, I can't see why I'd be any more annoyed by it than I would be by running a spellcheck on my work before posting. (Which I never do, so perhaps I will be 'visited' by the bot at some point!)