+1 (+2 if you include nuclear_eclipse)

I see no relation and no requirement for a constraint on these two fields.

Given the fact that it can be quite common for two distinct 'users' to have the same real name, and coupled with the tendency for some users to hide their real names with even more common pseudonyms.

Further, this problem grows over time for public trackers with thousands of users, the vast majority of which stick around only for one or two bug reports

Deleting users, while an intuitive first workaround idea is not valid, given it causes other issues.

I understand there is a configuration variable (thanks eclipse), and if this is the case, it should default to off (no constraint).

The original intent of the "feature" (0004198, 0003975) was to close a loophole where a user could masquerade as another user by setting their "real name" to the "user id" of another user and post comments. We don't allow the "real name" you select to match another's "user name".

As was pointed out, there is a config variable that allows one to duplicate "real names", and alter the display to be distinctive.