Hayato, leaded solder poses almost no health risks to users of it under normal conditions. Typical leaded solders are 60/40, tin/lead so even getting to the lead in the first place is difficult, any minor oxide layer is going to provide at beast trace amounts of lead, you'd have to grind it up and eat it to really have a harmful effect. I'd be more worried about breathing the rosin vapors than the lead content of typical solder.
Your cobler refrence isn't really applicable, because if it's actually plated you're talking almost absolutely pure lead, and they had it in their mouths for extended periods of time. I don't think tin dissolves as well as lead does in mild acids so what would happen is you would end up depleting the lead from the surface and end up with a solid tin layer that would no longer disolve. Not sure exactly about the solubility of tin in mild acids though. And that's only if you were deliberately moutihng on the stuff. Common soldering methods don't even require the physical touchign of the solder, it either comes off a spool, out of a spiral in a wound tube or similar.