Re: monosyllabic adjectives.
Sometimes, they take "more" and "most" (the following is based on The Oxford guide to English usage, 1994, and The Cambridge grammar of the English language, 2002):
- the following monosyllabic adjectives usually take "more" and "most": cross, fake, ill, like, loath, prime, real, right, worth, wrong;
- past participles (bored, drunk, lost etc.);
- in constructions of the type "more good than bad" or "more dead than alive";
- for stylistic reasons, e.g. "I am the more bad because I realize where my badness lies." (L.P. Hartley).
Martin Parrott (2000) adds one more case: when you want to make a specific contrast with 'less', e.g.:
A: Did she say it was less cold in the north of the country?
B: No. She said it was more cold.
Huddleston and Pullum 2002 argue that there is a difference between
(a) Ed is older than middle-aged. (his age is beyond middle age).
(b) Ed is more old than middle-aged. (metalinguistic comparison: Ed is more properly described as old than as middle-aged).
In the Longman Grammar of Spoken and Written English, there is a section on doubly marked comparatives and superlatives (7.7.5), e.g.:
She's a bit more nicer than Mrs. Jones (CONV)
It's much more warmer in there. (CONV)
The authors of the Longman grammar - btw, it's descriptive, corpus-based - say that "such forms are stigmatized and generally considered unacceptable - unless they are used jokingly in Standard English" (p. 525).
cf. Celce-Murcia and Larsen-Freeman (1999): "double marking of comparatives is a developmental phenomenon that never completely disappears in the informal speech of some English users" (p. 729).
There is a excellent paper where doubly marked comparatives and superlatives are discussed at length - Solomon, G. 1994. A more closer look at comparatives and superlatives. Unpublished paper. UCLA.