Nobody should hand over their ID to anonymous strangers on the internet. Unless and until Discord implements a centralized age-verification service, you should always treat any request along those lines with extreme suspicion.
Anyone can create a Discord server. There is no background checking or vetting of any kind. Yes, the odds of any particular server owner or moderator being a scammer are low, but being a victim of identity theft sucks, and it's never worth the risk just to chat about a porn game.