The most obvious solution to this is not to count posts of less than 50 words towards post count. (19 words)
Problem solved. People can still make short, one word posts - they just won't contribute to post count. More importantly, the required '50 posts' that people need to make won't happen nearly as quickly, as short posts won't bump the number. (40 words)
Barring that, penalize the advertisers. If an advertiser is generating enough income from posts here, then they can do a better job of checking people using their signatures. (28 words)
(87 words in total)
This would require more staff to moderate this though or the signature advetiser to moderate this because it would take a very long time each day to find out who is posting less than 19 words and who isn't.
+1
You could limit the font size and colours for the signature, that's all you could do without constantly checking new posts!
First - your post clearly demonstrates that you have no idea how paid writing works - which is fine. The (19 Words, etc) is simply giving you a visual spot of approximately how many words a post is. An advertiser (not a mod) can easily look at posts and see what they will or will not pay for without actually counting the words. I can sit here all day and tell you within 5 words with content of 50 words. If the forum code that tracks post count can't be modified to track the words or characters per post, then the advertisers can eyeball it. They will quickly get a handle on who is worth paying and who is just crap.
However, that just highlights the problem with this entire thread. None of you really grasp how paid writing works, and so you're applying solutions from your own perspectives that simply aren't going to be effective long term.
Short of eliminating signatures, you aren't going to fix the problem by changing signatures. Instead, you're going to drive off users who would make decent posts to earn a buck - which will only serve to increase the amount of crap in these forums because you're just adding incentive for the third world to make more shitty posts.
Allow me to explain (and really, I am not being an ass, so please forgive me if I come across as one - that's absolutely not my intent).
Third world countries - the ones you see the ads on TV that tell you how $1 a day can feed Sally, or whatever, are actually places you can live for less than $1 a day. You can feed a family for $1 a day in most cases. So that means anyone who has access to an internet cafe (a room filled with computers, all connected to the internet), can go from cafe to cafe in their city (let's assume 7 cafes), and make 14 posts a day on their accounts, even commenting on their own posts from other accounts - or creating foolish threads just to generate more fodder for them to comment on.
That means that in two weeks, they can have 14 accounts rocking the forums, each one making a collective average of 1 post per day. With the post minimums they way they are, those posts can be more or less crap. Every cafe has a different IP, so there is no way you will nail them all. At that rate, someone creative could spend their one day in each cafe, drinking tea (which is so cheap it qualifies as almost free), and making worthless posts about nothing.
The truly creative could one up it even more. Then there are those who +1 their trust in the process (for the truly entrepreneurial). There are some higher level users in these forums I've tracked and been warned of by others who do just that. Look at the trust of some users, and then skim their posts and - surprise - you find whole one sided conversations, with the same tone, character, and prose (or lack thereof in some cases).
So, at the end of the day, you either eliminate signatures, in which case your forums more or less die because your advertisers move away as the forums become a closed group of people increasing their own trust levels and posting crap, or you look at the issue from the perspective of people posting crap, and move it out of their range. When it is no longer possible to post crap, people stop posting crap (outside of the trust system abuse). Plain and simple.
Anyway, good luck with staying relevant in a sea of turds when you've just added incentive for more turds to float out in the forums.