Discord implements 'boosting', gating superior quality (and emojis!) - Discord once more proving to be like any other VoIP service, except twice as 'cute'.

Well don't I look like a fool.

Yeah, streaming data in general is a juggling act. Streaming data real-time even moreso. Good compression is an art. That Vorbis + Speex is interesting though.

Reliability isn't really that important for real-time voice chat. It's one of the times UDP actually makes sense because a bit of lost data isn't that big of a deal. Reliability only becomes a problem when there are large gaps or drops in data, or when there's a disconnect. That's more of a socket programming issue than a file-format and bit-rate issue though. If you want as close to real-time as you can get you use UDP because of the decreased overhead, but if the net is really unreliable where you are and UDP looses too many packets, a TCP option may be a necessity. Like you said, balance. The net is a strange beast with a lot of clever engineering too many people take for granted.
There's two types of reliability. At the codec level it's better that it goes robot voice than completely indistinguishable but a music codec would never need that feature.

At the network level initial setup is done over TCP but then they start blasting each other with UDP for less delay. This is also why it's super common for VOIP to connect but one side can't hear the other if the UDP packets are blocked or perhaps you roamed APs mid call and they're now going to the wrong place.
 
Discord desperate for shekels? Isn't what the glow in the dark CIA niggers paying them is enough?
 

IMG_20190605_081709.jpg
 
Back