I don't remember seeing this before. I just edited a block of code to be indented four spaces, because it was obviously formatted terribly without the code block formatting.
Eeeeek! Is this new? I thought 2k+ users weren't limited on how minor their edits could be....
Searching meta for "You made too few changes to the post to improve it" did not bring up any results, and I've never seen this before, so I suppose it's new?
EDIT2: Wait, the original revision now contains blockquotes. It didn't when I saw it first. The OP must have edited in the grace period. Hmm, maybe that's why! Maybe it has something to do with editing in the grace period while I was editing. Is it a reword of the "your edit must improve the post more than the previous revision," maybe?