If this is a design flaw, it's a massive one. If it's a bug, it should be a priority considering the serious cancer this community suffers from.
When I mute a person who suffers from a severe IQ deficiency and wishes to cope with it by constantly yelling utter nonsense in their mic, effectively preventing me from hearing footsteps while decreasing everyone's desire to see people below a certain IQ limit be processed into fuel; I would REALLY, EXTREMELY appreciate if my mutes remained instead of being deactivated a few minutes later for completely unknown and illogical reasons.
Seriously.
If I mute someone for very obvious reasons, I do not wish to hear them 5 minutes later.