As of today, every participant that has been a part of the signature campaign can remove his/her signature without any repercussions.
As for Twitter Bounty stakes and its calculation, here are some insights. Maximum number of retweets for period 1 to period 5 is 28 (max 2 retweets per day times 14 days equals 28). Everybody who exceeded this number will have only 28 stakes, no more. For period 6 maximum is 10 (max 2 retweets per day times 5 days equals 10). As for minimum number of retweets for period 1 to 5 it is 6 retweets. Every user that has 5 or less, he/she will not be eligible for the bounty in that particular period. For period 6 minimum is 3, because it lasted only 5 days.