The constant +o/-o is annoying, but only a problem for chat clients respecting the MODE messages, which Twitch-specific IRC clients really shouldn’t do IMHO. They’re batched and don’t separate channel mods from those with global moderation privileges (global mods, admins, staff) who aren’t even allowed to moderate the particular chat in most cases.
The viewer list is not properly showing mod status on all requests at the moment as far as my quick testing can tell; it’s listing mods under normal viewers instead in a lot of cases too.
/mods showing empty usernames is an old issue dating back over a year at least.
Also keep in mind none of this behavior is actually documented in the first place. Changes can therefore happen without documentation as well. (MODE is documented as a user gaining or losing moderation privileges in a channel; still as accurate as it used to be, just spams it more often.)