I wouldn't say the paid signatures increase the likelihood. It makes it so that you degrade the quality of your posts as to farm the signature campaign's money, as opposed to writing larger posts. A lot of people think it's quantity over quality, and most times they can get away with it.
I'm not trying to insult the mods; they do a good job with what they do.
I personally believe, however, that as long as your post isn't a single line, and it contributes
substance to the discussion, instead of being a neutral post, such as
"Oh that's nice. I think that would be a pretty good idea for the community to add"
Short posts aren't always bad. They need substance, however, to justify them being short.
If you can write at least 3-4 sentences, that have some kind of quality to them, they should be acceptable.
I have to ask... How much are people making from signature ads?
1 BTC a month? per year? ever? Some honest ball-park estimate would be appreciated.
Depends on your rank. People can hypothetically make anywhere from 0.16 (Which I
could do, but I choose not to) to 0.64, which is what the highest-paid member posting the max amount of posts in a month could make. So you could be making 5 BTC/year if you constant max our your post count.
People could be maxing counts for that very reason. And that could be why you see signature post spam...