I wrote:
@Tim: By "feature" I mean having values for column user.user_registration filled for DB replicas accessible from Tool-Labs, if possible. As Oliver has suggested, I don't see any reason for this info not being available, as it is already public from Special:ListUsers.
[...]
The information from Special:ListUsers is already available in column user.user_registration. Where this column is NULL, Special:ListUsers doesn't list any information either (cf. https://en.wikipedia.org/w/index.php?title=Special%3AListUsers&username=...).
Felipe?
Tim