In context:
His confusion about English usage is ___, because he is a native speaker and he is an English expert.
I find the word 'incomprehensible', whose defination in Collins dictionary is:
- incapable of being understood; unintelligible.
That seems doesn't fit the meaning of a word I am looking for to fill that blank, I want a word that mean 'it almost doesn't make sense to understand', not because 'it's too difficult (like a math puzzle) to understand.' is there a more precise word for that?
Expressing (mock) disbelief as a way of criticising something which is poorly done or inappropriate is very common, so there are a lot of words for it.
The most idiomatic is probably one of unbelievable, unfathomable, or unaccountable.
"Unfathomable" is metaphorical, and means investigation or measurement would not reveal the answer. (The metaphor is measuring depth from a boat with a weighted line - unfathomable depths are those which are too deep for the line to reach).
"Unaccountable" means essentially the same as "inexplicable", i.e. there is no explanation which could be given.
Any synonym of those is probably also suitable: Incredible, unthinkable, inconceivable, preposterous and so on. Each has slightly different connotations, rhymes and rhythms, so you can pick one to suit your needs.
Instead of looking for a direct opposite, take a broader look at what you are saying.
It's the usual thing that non-natives get confused about language.
The opposite of usual is ... odd, unusual, peculiar, ...
If choosing to say "peculiar", I'd say, "I find it peculiar ..." But I would actually need another reason for finding this kind of thing peculiar.
I find his confusion about English a little
peculiarodd, seeing he is a native speaker and a graduate of Yale.
Well, no, "peculiar" is about as extreme as "incomprehensible" would be.
How about an opposite of another near synonym, "logical", thus, something like "puzzling"?
