All your questions and concerns are good one... at least this time though I feel like more people are stoked on it!
I think the commas would be a good addition definitely to make it easier to figure out.
The problem about the massive numbers is tricky... people want to see it change, and they hate it when everyone is so close together, but with almost 110,000 members, rating out of 1,000 would leave many people right together.
If we had decimals, it'd be an equally big number just with a decimal in it.
Sometimes if you rank someone a 7 and their karma goes down, that might mean that they had a 10 before.
The issue of WHAT is used to calculate the karma is easy to change. So that one is something we can play with over time. However, each time we make a big change like this to the system, we've got to give it a bit to get used to it! Remember, anything new on the internet is generally hated at first, and then as you get used to it you'll see the benefits.
So give it a chance, use it and in a couple of weeks we'll re-assess!