Editing an OP shouldn't result in a thread bump. A lot of the time I just want to fix a spelling error or grammar problem without alerting everyone else I've suddenly updated the thread.
If you want to bump a thread that has been edited, bump with a simple "the OP/map/thread has been updated, relevant information is [here]." That's easier on the reader for 1. because they don't have to re-read the entire OP to find the edited information, and 2. it assures the poster makes a useful and relevant edit that they themselves want to bump. Automatic OP bumping via OP editing is useless.