I have known that an adjective of a positive degree is always omitted in a subordinate clause of a comparative sentence like the following
*He is taller than I am (tall)
I happened upon a phrase which doesn't omit such an adjective like the following.
used before adjectives and adverbs to say that something is more than is good, necessary, possible, etc. (Definition of a word 'too')
Source is from Oxford Leaner's Dictionaries.
I think the phrase should be changed to the following.
used before adjectives and adverbs to say that something is better or more necessary or more possible, etc than something is.
Adjectives are included in the subordinate clause of conjunction 'than' like the above.
I'm not sure if I have had a wrong information. I want to know why the subordinate clause consists in such an adjective.