I have always been a fan of the adagium 'lurk moar', so I think that that is a good idea. Spam is mostly linkspam anyway, I doubt there is much comment spam around. It might be worth keeping an eye on what kind of accounts promote what kind of accounts, because you might have someone spending some actual time here and then just promoting all of their bot accounts.
Maybe to continue the 'hubski as a bar' analogy, you could use the word 'welcome'? I imagine a bar regular welcoming a young padawan to the table.