Thank you!
This is a very thorough answer to my question, and was what I was looking for. This is actually a lot more interesting than I thought. It seems like the invitation distribution has some intelligence to it. And, if I understand it correctly, this is actually built into Merit Core? In other words, this is actually part of the consensus mechanism.
Quite interesting.
How does the system prevent people with the highest CGS from effectively getting all the invite tokens?
Yes it's built into blockchain, part of consensus.
People with higher CGS usually use most of the invite tokens, so it's fair to distribute it to them based on that key. Anyway, algorithm for generating invites are dynamic so there won't be situation when no invites will be left, if more invites are spent, more are distributed. It can be hard in short-time when many invites are used, but next days also many invites will be airdropped.