[Donny]

What I think is, no matter what the rules says, it's always good manner not casting BE-retreat when you are able to do so, cuz it will cause conflicts.
It's unfair to say everyone casts this is bad, though.

Well, considering MoD I'd say that it's not a problem itself just like all the other GEs. BUT, it causes a serious bug, that's the difference makes all the opponents cry.
For example, in GhostBat i'm currently playing, DryaUnda (MA PY) and cipher (Agartha) had a battle. The MoD bug hit, crushing the game (even llamaserver failed to generate new turns correctly, llama fixed it though).
I really appreciate DryaUnda as he casted MoD without retreating, however he was beaten and his mage routed. But MoD was still there, causing bug making all the agartha's MOs disappeared.
Similiarly, I guess if two super SCs have a battle but can't kill each other will cause the same bug, not tested though.
MoD is a very possible way to causing bugs that's the reason it should be considered different than the other GEs and be banned until it's fixed.