The degree of comparison in the form “as + adjective + as” is positive, not comparative. Recall that there are three degrees of comparison—the positive, the comparative, and the superlative. The positive degree uses the basic adjective in the “as + adjective + as” form, as in “Her grade in Physics is as high as my grade in English—95%.” Strictly speaking, in the positive degree (the degree of equality, as you mentioned), there’s no difference in degree at all because the things being compared are equal in the aspect described by the adjective.
The comparative degree is, of course, used for comparing two things, as in “Mt. Everest in Nepal is higher than Mt. Kinabalu in Sabah by 4,445 meters,” and the superlative degree for comparing three or more things, as in “At 8,550 meters, Mt. Everest is the highest mountain peak in our planet.”
As we know, most comparatives use the suffix “-er” while most superlatives use the suffix “-est,” but there are other ways of expressing comparison depending on the spelling and the number of syllables of the adjective used. When a two-syllable adjective ends in the letter “y,” in particular, “-ier” instead of “-er” is used in the comparative, as in “We hope to have a merrier Christmas this year than last year”; and “-iest” is used in the superlative, as in “His merriest Christmas must have been in 1982 when Gabriel Garcia Marquez won the Nobel Prize for Literature.” However, when the adjective has more than one syllable, “more” is used in the comparative, as in “Broadsheets are generally more reliable than tabloids as information sources”; and “most” is used in the superlative, as in “The pork barrel scam is easily the most shocking manifestation of unbridled government corruption in living memory.”
