so + excellent

Yes. There are different levels of excellence. Had you said "so perfect" there would be a logical problem, as something is either perfect or not.

Yes, the sentences are correct.

They are correct, because it's based on a personal opinion.

Okay, but I was only commenting on the grammar.
I was commenting solely on the grammar.
Excellent is an adjective like any other.
No mystery.
okbye.

The main or traditional meaning of 'excellent' is the best, either among a group or of a kind, or overall. It comes at the end of a range. Adjectives that are at the ends of ranges are not gradable, whereas the ones in between are.

Consider:

Freezing - cold - cool - warm - hot - boiling
Excellent, good, average, poor, bad, terrible

The adjectives in between the ends of the ranges can be modified with adverbs of degree such as 'very', but the ones at the ends cannot. Thus a careful native speaker would be uncomfortable about using 'very excellent'. There is a secondary meaning of 'excellent', which is 'very good', and again, the 'very' would be redundant.

Thank you all very much for your answers.

Hello contrex,

Thank you for your explanation. But what about "so excellent that..." ? It seems that the construction is possible and grammatical, isn't it? It would be nice if you could tell me why.

All the best

You could say 'his work was so excellent that he was immediately promoted' but because the word has two meanings, 'best' and 'very good', a tension is created. The best I can do is to say that 'grammar' is not everything, that successful use of language is more than treating words like Lego blocks. If you mean 'so excellent that' to mean 'so widely considered to be the best' then personally I feel it would be better to say it in that way, because a native speaker would possibly perceive the awkwardness of grading a superlative. If you mean 'so very good' then say that.

Thank you very much, Contrex. That helped.

Best regards