I'm not sure whether or not I would describe them as edit-trolls. If the user has the badges and no rep to gain, I can only assume they are trying to address what they see as a "problem". No matter how minor.
Do I agree with the particular edits? No. Too minor and incorrect. But I see no evil motivation either. Editing is a bit of a personal thing anyway. Yesterday I encountered a moderator on one of the sites editing a question into shape, and at the same time highlighting sections in bold. Personally this ticks me off, because I see no need for the bold formatting. But whatever our preferences, we're all trying to improve content where we see a problem.
And exactly for the case where a user wrongly edits a question, we have a rollback. The problem with edits is that there's nobody really teaching us what good edits are and what are bad ones. There are no clear guidelines. There is no document outlining various scenarios and how to act upon them. Where your company might have a strictly adhered to code-style, there is no such thing for SO posts. (Nor do I see how that could be created really, besides some very basic rules. Don't format things as code when they are not, for example) Yes, we initially have the review system for newer users. But to some extent it seems to be flawed as a teaching tool when pretty poor edits are getting through. (Thereby validating the user in their edit).
What can be done? Well, you could always @reply the user telling him that the edit really is too minor and incorrect, so you've rolled it back. Perhaps they'll pick it up. Don't let this spark off a long stream of "how to edit" debate in the comments though. Take it to Meta perhaps, or point to one of the many discussions on appropriate and inappropriate editing already here. Or just undo the edit and let it slide.
I don't think these users are necessary trolls. But editing is a tricky thing. As much as we have users asking good and bad question, we have users making good and bad edits. Or unnecessary ones. Or ones we even on an aesthetic level disagree with.
The only real "solution" I see is to lead by example. Try to make the best posts and best edits we can, hoping that some of the style will rub off on others. But luckily we already have the tools to deal with situations where this is not the case.