The original Reddit post somewhat overstated the nature of "several people expressed concern." Nobody told him outright that despite what he might think, he did not really know Scots. That one screenshot'd, anonymized conversation was the one time something like that happened in seven years - but that could very easily be read as a criticism of those specific translations, not of his work as a whole. It seems as if the Reddit OP was the first person to notice the editor's systemic incompetence and failure to understand the degree of his lack of fluency. So... no, I don't think he ever made this "second and bigger mistake", aside from general massive naivety. After being told explicitly now, he's certainly ashamed and horrified at wasting so much time on his own personal dialect of Scots.

Looks like the situation is in hand now. It's a pity it needed to get to this, but I don't think it needs to go further.