Wouldn't it be a better idea to make the Introductions a spam section, meaning no posts would be counted here, so people can welcome others and such without being accused of spamming?
We're pretty laid back here in the Scanlation, Introduction, and Boredom Zone forums as far as "spam" is concerned. They all serve their purpose, we're always going to have brief posts in each of those, whether it's "welcome!", "thanks!" or something else. A post count is just a number after all, if it encourages participation in the community then I think it's fine, so long as it stays in the respective areas.
Anything we think isn't worth our member's time ends up in the graveyard anyway, the only board here where posts do not count.