Myrdin will be good he can rest a bit around this time.
I can't comment much about this topic since I not understand clearly what Myrdin and Mindrunner type.
For real during those discuss I think they just thowing some joke to each other.

Those word like mofumofu is some kind of sound symbol.
It do call omonatope or something. A lot of those word doesn't have exact meaning.
And it's normal that someone not familiar with japanese language will think it's a some kind of slang.
About sound symbol, it's not my comment, it's my junior one.