Let's see it this way.
Those who just want to steal are by certain not really mappers. A true mapper would decompile it and look how it's done (If he actually went to such lenghts to decompile it). Then try to do the same in his map. And will probably credit you too for it. That's how the community works.
And with all the brush errors ,they're usually experienced if they get it back to normal again.
And if they're experienced then they most likely know these "decompiling rules" I just mentioned.
You can add a few brushes to create a signature in a uttermost corner of the mapping grid. Not many would notice it and you could then have proof against them if they ever copied it. That's what we did in Duke3d.