Well, i think 10 - 15 posts should be enough to figure out if person a spammer or not.
(i bet the point to allow sigs only after 30 posts was because of this)
Spammer can easy make 50 posts (so, it does not make sense), but for real posters takes some time.
Note that sigs are impotant not only for spammers (lol) and this could be the reason that some members will refuse to chat. (just my opinion)
I don't know whether this rule was implemented to try and cut down on the spammers, but I doubt it very much, what's to stop a person from spamming after they have sig rights?
All forums have rules that need to be kept to, whether we like it or not.
You are allready paid to post in this forum, why should you get instant free advertising aswell? If members were able to have sigs at the start you could very well get a lot of hit and run posters that are only interested in promoting their own programmes and not helping the forum grow.
This, of course, is just my oppinion, I have not asked why there is a 30 post rule before signatures are allowed, I just got on a did what I came here to do, and that is post.