So, I'm not sure how to word it, but I hear majority of people say des-ne and des-yo. But following this: What are the rules regarding "mute vowels" ("u" after "s" and "i" after "sh")?
It seems that you aren't actually supposed to drop pronunce the u. So my question is, is this some type of special case, or do people just like to make the u silent. If I said desU-ne or desU-yo, would that be ok? Would that sound feminie/mascuine/strange/cute/serious?
Would that sound feminine/masculine/strange/cute/serious?
It would sound... accented, to some.
In very rough terms, Japanese has two major dialects/dialect groups, termed "eastern" and "western".
Eastern Japanese is largely characterized by the standard Japanese spoken in Tokyo1. Among other things, this normally features the devoiced u-vowels you're describing (not necessarily silent), the "compressed" sound for the u-vowel when it is voiced. Inflection-wise, it features everything you (most likely) see in your Japanese textbook.
Western Japanese is typified by what's commonly just thought of as Kansai-ben. There exist finer distinctions (between Osaka and Kyoto dialects), and broader generalizations (the Kansai region vs. everywhere west of that); but that's the archetype.
Kansai-ben is marked by differences in pitch-accent, rendering of sounds, and the actual inflections. Historically, there was a period when Kansai-ben was the prestige dialect; in more recent history, the Tokyo dialect has been treated as "standard".
(That's about the end of what I can cite. The rest of this is based on my subjective interpretation of an inherently biased and personal listening input.)
In particular, it's common for u-vowels that would be devoiced in Eastern Japanese to be fully voiced. and for the voiced u to be uncompressed - i.e., the Kansai-ben vowel chart is even more like the Spanish vowel chart, with five simple, ordinary, "pure" vowel sounds. The top answer at the other question says that おう commonly gets rendered as お rather than おお, but what I hear more often is that it actually becomes おう, and then the う is subject to un-compression and even significant rounding. It gets to the point where a -ましょう ending on a verb sounds a lot like a southern American saying "my show", and the u-vowel in です gets prominent emphasis.
In the modern era, the question of "prestige" is not so straightforward. Kansai-ben seems to be gaining popularity and "coolness" nowadays from what I can see, especially in the entertainment industry.2 On the other hand, I understand that it's still used in anime to signal that a character is supposed to be, shall we say, on the less sophisticated side.
1 To my understanding, pretty much everywhere north of Tokyo is fairly similar accent-wise. It does drift further from the standard - northern Touhoku dialects has some major phonetic shifts, and things are different again on the island of Hokkaido - but speech patterns here are certainly more similar to each other than they are to Western dialects.
2 I commonly hear these features used by MCs, Vtubers and other タレント - and I guess it's not just me. The sound shifts seem to be more common than the inflection changes; やばい->やべぇ is common, 分からない->分からん less so, although I think I've heard わかんない. I am pretty confident that all of these features reflect a consistent "Western Japanese" dialect, although it might be a different/more specific one.
