It would take something monumental to happen with users signature spamming or alike for 1xbit1.com signatures to be banned from this forum but their account would most probably be not.
On the other hand, 1xbit doesn't encourage spamming and enforces the usual rules followed by other signature campaigns in this forum which is why they haven't been banned yet.
Actually, whether that campaign encourage spamming or not, some weeks ago I caught a couple of members of that signatura campaign spamming so they could complete their weekly post quota, you can find more information on this Meta thread:
https://bitcointalk.org/index.php?topic=4720640.msg60624862#msg60624862Personally, I believe it makes sense, if a campaign is full of people who do not care having negative trust then they will not mind to spam when they believe itis necessary.