My point being, if you have never been banned, you then get a paid advertising signature and continue posting how you have in the past, you aren't going to get a ban just because of the advertising signature. If you let your post quality deteriorate to meet quotas as tends to happen, then you do risk being banned.

There are people who just don't post very well in general, post "too much", or don't really have anything to say, they just like to participate in the community and post. This itself is fine. But when you add an ad to these kinds of posters, it's difficult or impossible to tell if they just aren't quality posters or if they are attempting to boost their post count. I used to err on the side of caution here because I do not want to ban the former, just the latter, but too many of the latter are slipping through the cracks because it's very difficult to gauge someone's intentions. This is the main thing that has changed lately.