Maybe an idea for signature campaign managers should look into is actually having a min word limit on posts saying min words per response 10 to 15 etc or if under this posts will be future inspected to check to see if qualify as a quality post or not. That way it would sort a lot of problems out for many campaign managers that are running current ones. I have only seen a few people being removed from signature campaigns and most them where for posts being too short, spam, off topic, arguments, scammer, getting banned, removing signature part way though and then making some excuses up that wasn't them.
This idea is already being implemented by Bitmixer.io although it measures characters rather than words (the limit being 75 characters).
Trading accounts can be stopped it is what security measures are in place. For example if IP changes and location changes on an account it could easily be locked and then have someone contact from the original email it was made and also provide documents to provide it is their account or give veiled reasons as to why their was an IP change. If it constantly changes to different locations then that account can simply be suspended. I have all sorts of things in place to stop this happening from exchanging accounts to people selling them. Had all the excuses given me and I simply ban. Their is no good reason as to why someone should sell an account on other than to make profit from it or to be illegal activity or something that does not quite add up to the point of selling trading or exchanging an account.
IMHO this doesn't sound like a good idea at all, and I might even go so far as to say that it goes against the spirit of Bitcoin. Many people here are reluctant to give out their phone number let alone documents proving identity, address, etc. In the past year, I changed my location 3 times and my IP address 4 times (I'm a student). Multiply that by the thousands of members here and it would quickly become infeasible.