Answer:
One View
The test of any utterance in a language is whether the listener can understand what the speaker has said.
I can understand the expression 'a little bit pedantic' - so 'a little bit pedantic' is a correct use of the term.
Another Opinion
I can understand the term 'a little bit unqiue' but that's not a valid sentence, as something is either unique or it isn't.
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Another Opinion
'The test of any utterance in a language is whether the listener can understand what the speaker has said.' - Not so. Me no spick Eengleesh is perfectable comprehensible but is not very good and make make the speaker the object of amusement,
I take the question to be whether pedantry is in some sense quantifiable, or whether one simply is or is not pedantic. Surely, it is perfectly possible to be somewhat pedantic at times.