I just gave the google hits to show that the forms do occur often enough. (Another older form I just read was oftnest.) You said a native speaker of English would not use the forms quieter or quietest. I suggest that many native speakers do, myself included. And you telling me it's wrong is not right. I can also not think of any three or more syllable words that I could use -er or -est with. Using quieter as in "she is the quieter of the two" is exactly as grammatical as more quiet in "she is the more quiet of the two". Except to my ear the latter sounds a little more stilted than the former. Using quieter or securer is not the same as mistaking one lexical item for another. You yourself said that these "rules" have exceptions. We all make mistakes. You gave a "rule" for forming comparatives and superlatives of adjectives ending in -y that was incorrect. In a sense I found your mistake worse than some teacher misspelling a word. You probably don't. It's OK, because this is an informal kind of place and people post all kinds of English on it.
