First of all, I’m assuming this もっとも is 尤も. If you think otherwise please let me know! Assuming that is correct,
I’m also inclined to think it is the first definition here, that is to say, the one that means the same thing as でも, as I was told this でももっと is not unlike しかしながら ( which I had never heard of prior, but according to a Japanese person it exists).
So! If it does indeed mean “but” as でも does, then why put both? 「でも」か「もっとも」だけに比べて、含みはどう違いますか？
If you’re asking for interpretations of a sentence that starts “but” it would be helpful to give context so we know what he’s saying “but” about…
Anyway, I read that as sense 2, ie “But that’s understandable/reasonable/rational” – the next dialogue balloon then gives the reason why it’s understandable.
But that second definition is an adjective as in (尤もな意見) , not an adverb, so surely it can’t be that right?
It’s a noun here (the copula has been dropped).
What copula?
I mean, I interpret this as being equivalent to saying でも、もっともだ, but the だ has been dropped because this is pretty casual speech.
hmm… maybe so!
