Editing other users posts is not limited. As a proof, just run this SEDE query.
Top daily editor at the moment is hakre with 2820 (!!!) edits on a single day, December 24th 2012. You can verify this by sifting through the user's revisions.
The system probably counts on the fact edits bump the questions to the front page so it's easy to detect abuse and in such case suspend the offending user.
As for editing own posts, which can be done even with 1 rep it's limited for a good reason and the exact algorithm of reputation scaling is kept secret for a reason, most likely to prevent abuse, even by high rep users. Best description can be found here:
Broadly speaking, the higher your reputation the more edits you'll be able to make before running into this anti-vandalization cutoff. Past a certain point, the limit will be removed altogether.