In my opinion, such edits are not just fine, but positive, as long as they actually improve the post. Typos should be corrected, pointless salutations and signatures removed, and so on — and not just on the newest questions.
There are badges for curation of old questions for a reason, and that's not "gaming the system" except in the sense that the system is meant to be a game which encourages editing and improvement. And you don't have to take my word for it — this is generally consensus for Stack Exchange overall.
It is pretty annoying when edits correct just one typo and leave others intact. If you're fixing a spelling error, might as well also take the time to adjust the tags and improve the title so it describes the actual question specifically. There used to be a "too minor" reject reason, but this has been replaced with the much more strict "No improvement whatsoever" — this seems like a strong suggestion by the Stack Exchange overlords that even small edits should be accepted if they go in a positive direction.
That said, if you are making a small edit, it would be most awesome if you think about the post as a whole. Nice titles and tags really help the discoverability of old questions. (If you're looking at the review queue, consider the "improve this edit" option, too.)