I mostly make vector art/traces. Since vector images are made up of objects, they can be easily modified. Sometimes I make a vector trace and submit it, then later go back and improve it in some way. (e.g. #202087; since posting that I've made several improvements to shading and general shape.)

Does e621 provide any way to replace an image with a newly-created improved version? Right now, I think the only way is to delete the original and upload the new version. But that counts toward the user's deleted post count, and discards all of the votes and comments of the original, so it's not ideal.

I think this is a bit different from cases where an image is removed because a better version (higher res, better scan, etc) is posted, since in this case the better version didn't exist when the original was posted, and comes from the same artist.

Short answer: no.

We can only delete the original after the new version is uploaded. Faves can be preserved.

Well, it'd kinda suck to have a bunch of deleted posts on your record just from replacing them with better versions... I guess if the better versions are accepted, it balances out, but are there any penalties for having a lot of deleted posts?

Only if you have an absolutely absurd amount of deleted posts.

RenaKunisaki said:
are there any penalties for having a lot of deleted posts?

For every 10 posts that get approved, your posting limit increases by 1

For every 4 posts that get deleted, your posting limit is reduced by 1

You do make a good point about making allowances for updated versions that don't affect your posting limit Rena, especially if the content belongs to you
I think there's a way to modify one's posting limit, but you'd have to ask one of the staff about it to be sure

Admins can make exceptions to the posting limit if need be.

Admins can and do on rare occasion boost a users posting limit if we feel they got screwed on it, though it will only be boosted to "Default" levels [10 posts}