I always find those annoying to copy (we use a lot of shared credentials, like when the customer gives us 3 accounts with different permission levels to pentest an application with) and it also simplifies the command to not have to specify all those symbols. You can also avoid the whole `fold` thing by just telling `head` to give you a certain number of -c instead of a certain number of -n.

    </dev/urandom tr -dc a-zA-Z0-9 | head -c 16

(Then again, you were proposing an alias, so then command complexity/memorability doesn't really matter.)

Security level: log((26+26+10)¹⁶)/log(2) ~ 2⁹⁵ (95 bits of entropy), comparable with adding those 12 extra symbols: log((26+26+10+12)¹⁶)/log(2) ~ 2⁹⁹. (Adding a character makes more sense than adding a symbol if you want more security, all else being equal of course.) If a stupid application still has outdated password requirements (thankfully this is rare among the applications I use) then one can of course add the classic ! at the end.