I don't know if you got a response to this post in the other comm, but since you didn't get one here, I'll mention that Kat Kincade talks about this question and Twin Oaks's five-year experiment in a variable labor credit system in her book Is It Utopia Yet?
pp 30-32 (with a related discussion of assigning undesirable tasks from 32-33).
They tried two systems: one in which each job had a fixed rate (eg washing dishes = 1.2 c/hr; cleaning toilets = 1.8 c/hr, etc) and another in which individuals set their rate (i like making tofu, so I get .8 c/hr and you don't so you get 1.3 c/hr, etc).
The experience she reports is that the idea of variable credit had some traction but that the fixed system was just as inequitable as a universal rate (because if you like digging ditches more than balancing checkbooks and I feel the other way, then how do we find the right rate?) and the individualized system was too susceptible to manipulation.
I (who have visited communities but never lived in on one for more than a few weeks) tend to agree with TO's eventual conclusion that a variable credit system is too fraught to be worth the headache. Perhaps it would help to shift the focus from "how much is an hour worth?" to "how do we make sure that everyone mostly gets jobs they enjoy / the unpleasantness is spread around about equally?"
If you don't have access to the book, let me know and I can send you a scan of those pages.