Donors have the ability to:
- Talk while dead
- Call votes on other players (Slay, mute, teamban, and gag)
- Change chat color, name color, and tag color
- Resize self, set voice pitch, etc.
So your question asks:
are donors supposed to be muted when dead because I don't think they're supposed to be muted when dead but they are
No, not really, as raiden said:
Donors can't be muted when dead.
I hope this answers your question, if any mod or admin would like to give more insight into this, they can and I hope it helps the gent asking the question.