Hm. I've never actually questioned editing, so let me do a few quick checks about editing changes.

In the meantime I can tell you that our volt count system is meant to ignore BBCode and not grant volts for it, though there's always the risk that a bug is making that different. I'll check in with baz about edits to see what's intended to be happening, though!

So let's see. I checked with Baz, and code as intended is supposed to be a system where if you remove characters from your post that were valid and granting currency, you're supposed to lose the volts that you spent. It appears that the code is a big buggy at the moment--adding characters doesn't affect anything, but any post that removes characters, no matter how many, appears to deduct a single volt.
I've passed this on to Baz, since I don't think it's working as intended, and I'll move this to bugs so he can track it.
Thanks for letting us know!