I think denouncing is an incredibly bad idea especially as the foundation of VOUCH seems to be web of trust. If you get denounced on a popular repo and everyone "inherits" that repo as a source of trust (e.g. think email providers - Google decides you are bad, good luck). Couple with the fact that usually new contributors take some time to find their feet. I've only been at this game (SWE) for ~10 years so not a long…
I'm guessing denounce is for bad faith behavior, not just low quality contributions. I think it's actually critical to have a way to represent this in a reputation system. It can be abused, but abuse of denouncement is grounds for denouncement, and being denounced by someone who is denounced by trusted people should carry little weight.
OVER-Denouncing ought to be tracked, too, for a user's trustworthiness profile.