No, I don't think the adjective 'commie' was meant for the creator of Krtek, it was meant for the mole himself. The commie mole. Not 'the commie's mole.' There was surely no insult implied. Not that I could see. Just a reference to the fact that he was a cartoon character from a satellite nation of the Soviet Union. Surely Krtek didn't discuss his politics much. Kids don't like politics.
I have never thought you could interpret it that way. Frankly speaking, I know hardly anything about the author but that he is the author. But it is the litle mole himself whose extenstive undeground activity is well documented. Perhaps it is matter of family tradition, for his whole family is reportedly living in underground for centuries. Stories for kids are not by the kids. Commies always liked preaching communism to kids, it was the only way to raise new PavlĂk Morozovs.
Oh I get it, I misinterpreted your first comment about Krtek. When you said ''underground'' I guess that was a reference to the fact that moles live their lives moving about under the ground. It is a nice play on words though. 'Underground' can mean committing acts/living a life outside of/outside the vision of authorities, for purposes of subterfuge and sabotage, etc. But I'm sure that's a term you are already familiar with, the Czech underground, French underground, partizans during WWII. So maybe I am still missing the point. Also the term 'commie mole' in the clip is a play on words, besides being a literal MOLE, a mole is also someone placed in an organization with the hidden intent to gather information or otherwise cause destruction.