It might not apply specifically, but it has tangential relevance because such adjectives are almost always two syllables, with the stress on the first syllable. There are other common adjectives that have this profile, and will be used in either way such as stupidest / most stupid, simplest / most simple, etc., both spoken and written in informal contexts.
I’m pretty sure you wouldn’t get this for common adjectives that don’t follow this pattern, (e.g., stress on the last syllable, such as alive, afraid, complete, etc.).
I have no problem with winningest, which currently has a red squiggly line under it as I have typed it, but don’t get me started on funner and funnest. Blech. And I think those are gaining acceptance as real words now -_-
I don’t see anything wrong with them. I admit, I don’t think I’ve heard “funner” in speech, but “funnest” sounds completely unobjectionable to me. Are there any other exceptions for one-syllable adjectives that don’t take an -er or -est ending in the comparative and superlative? I can’t think of any. While I’m always arguing against trying to use logic when discussing the English language, that’s a weird exception to me.
FWIW Merriam-Webster recognizes “funnest” as a superlative form of “fun” that is “sometimes” used.
I used to teach English overseas, and I remember the rule given by the textbook about superlatives. It said the “most <adjective>” form was always acceptable, but that adjectives of 1-2 syllables one could take the “-est” ending instead. Adjectives of three or more syllables should never take the “-est” ending. It said the “-est” form was generally the more common one for 1-2 syllable adjectives, but that when in doubt students should go with “most <adjective>”.
Being a native English speaker I’d never learned or even really thought about any such rule for superlatives, but this did seem to me to correctly describe common English usage. A girl could be the smartest and prettiest one in her class, but not the intelligentest and beautifulest…although I see Firefox’s spellcheck does recognize “beautifulest” as a word. Anyway, “most smart” and “most pretty” sound awkward, but “intelligentest” and “beautifulest” sound ignorant. I guess it’s because this sort of over-consistency (that is, consistently applying a language rule like “superlatives take the -est ending” that actually has many exceptions) is the sort of thing small children do when they’re learning to speak.
As for the OP, I don’t think I’ve ever heard to word “winningest” used before. Before opening the thread and reading the context I would have taken it to be a superlative form of “winning” in the sense of being appealing or attractive. As in, “She’s the prettiest girl with the winningest smile.” Using it to mean “has won the most often” sounds stupid to me, but I don’t follow sports at all so I can’t really judge how common the usage is.
I remember the rule as “-er” and “-est” is always OK for one-syllable words, never for three-syllable words, and it can go either way for two-syllable words (with two syllable words ending with an “ee” sound, like “pretty”, being okay with “-er” and “-est.”)