Okay, let me take a shot at this.
I actually like the status quo for regular enums, when repr() shows the type, name and value, and str() shows "classname.flagname", so I'd stick to that for converted flags. Even though this violates the rule of thumb that repr() should look like a valid expression -- perhaps a stronger rule of thumb is that repr() should show more than str(). Showing just (the str of) the value seems unkind, since e.g. showing '4' makes me think it's just an int. (Then again I can see that for *converted* flags that's not unreasonable.)
But yeah, backwards compatibility. However, I don't think we got any complaints about the `re` flags, did we?