"New" adjective in comparative form

Question

There's a rule about one-syllable adjectives that end in a single vowel and a consonant, that duplicates the consonant in the comparative form:

big --> bigger

hot --> hotter

I've been asking around to native english speakers and nobody seems to recall this specific rule, and the odd thing is it doesn't apply in the adjective "new":

new --> newer, not newwer

So, some students were wondering why "new" isn't considered an irregular adjective like bad (worse instead of "badder"), good (better instead of goodder), etc..

Usually I look up in a "A practical English Grammar" by Audrey Jean Thomson, A.V. Martinet, Oxford University Press - Fourth Edition to answer all my doubts, but this one keeps on puzzling me.

Answer 1

Your rule is too simple to be correct

1. Very few words in English have "ww" in them. In fact 99% of the words that do, are compound nouns that could be written as separate words or hyphenated. I think the only verbs with ""ww" are "bowwow" and "powwow" https://www.thefreedictionary.com/words-containing-ww

2. The letter "w" is a semi-vowel. Here's an article that explains further When Is "W" a Vowel?

3. I surmise also that there are few to zero doublings when it comes to adjectives ending in h, y and x

Maybe you could come up with your own rule?