If someone provides a good edit to my post, what is the proper way to provide feedback or thank that person? Is it necessary? I do not yet have enough rep to edit other posts, and expect that I will be reluctant to do so other than typos and minor edits, so I expect some positive feedback on an edit would surely be welcome.
TL;DR: Don't revert good edits. "Carry it forward". Write self-destructing short ping as thanks.
First, do not harm. Don't revert good edits. If an editor made an error, by all means fix it, but be aware that great editors may be right even when they might seem to the less experienced users to be wrong. That's what makes these editors great. So at the very least, do nothing and don't roll back a good edit.
Study the edits. Learn from the good editors. Read the history of the edits and review the comments. How do I view the edit history? Click on the icon [Show activity on this post] to the left of the question, below the vote up/down arrows. The icon looks like a clock being turned back.
Write better posts. Use the skills you have learned from good editors.
Edit your own and other people's posts. Carry forward the good karma and teach others. Leave places you visit cleaner than when you found them, but don't be nitpicky. Be nice, for the good editors were nice to you when you needed it.
Find nice, creative ways to thank the good editors. If you meet the good editors in person, buy them a beer. If you meet them on Stack Exchange or elsewhere on the interwebs, say thanks in comments. Be sure to delete your Stack Exchange comments later, after the editors have read them (usually in a day or so). This is because "thank you" comments are considered noise by others here on SE. You can also write under your post a short, self-destructing comment like this: "@rene Your edit was greatly appreciated and helped me to xyz after realizing abc!". Not finding the self-destruct option in the UI? Me neither! So I just delete the comment myself, manually, after they have read the thank yous, or in a day or so, whichever comes first. Note that some good editors even prefer not to receive the "thank you" comments. They are busy people. They consider their work as "nothing special", and there is a special place for them in the Great Stack Exchange in the Sky. For the truly outstanding editing work, consider awarding a bounty on one of their good posts.
Don't serially upvote the posts that belong to the good editor (that you find in the good editor's user profile). That's bad (oddly enough at first glance, but think what could go wrong here!), because that's against the rules. Serial voting will be automatically detected. And then reversed, also automatically. Don't learn it the hard way. :)
Don't serially edit the good editor's posts. Seriously. Instead, see the "carry forward" item above.
This post incorporated ideas from multiple posts, notably those by Don Wakefield, William Pursell, Nosredna, Hilarious Comedy Pesto, Shog9, Kevin B, Hans Passant, Paul Roub, MonkeyZeus, Rene, Kendra, πάντα ῥεῖ, Sam Hanley, John Montgomery, kenorb and others. See the current page and also the links below.
A thing you could do, related to this question is find a post of their's at 9 upvotes or something like that, and so long as you think it is a good answer, you could upvote them there. I wouldn't encourage upvoting a bad answer, but I completely understand the desire to show your appreciation.