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There is nothing wrong with anyone wearing a paid signature (I am wearing one myself). However I think the reality is that people with paid signatures tend to spam more and as a result should be held to a higher standard then those who are not receiving a specific payment based on how many posts they write.

This may not result in the 100% equal treatment for everyone in the forum, however it would likely be what is best for the community overall and would likely still result in everyone being treated fairly

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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.