The fact that you can argue it's not forbidden by any rule doesn't make it actually not shit.
I'm not. I'm arguing that the correct use of a word in English is derived from either:
1. It's original source
2. A corruption of it's original source
3. The general all purpose rule which is to grammar what default national ides are to national ideas.
Or to put it another way, since you mentioned it, what is the past tense of to shit? Shitted. What do people actually say? Shat. Why? Because it sounds like the irregular verb sit, which goes to sat. Does anyone actually care? Almost certainly someone somewhere does, but most people don't. Ethoses sounds wrong like shitted does, so people don't use it. If it really bother's OP, I will switch to some other correct sounding one though. Ethe probably.
And in case it wasn't obvious by the fact that cromulent isn't actually a word,
. Is what I was referencing.