yes the rect variable is called myRect, the udg stands for user defined global, a prefix all variables used in GUI have when used in Jass.
Point and Rect variables are set and removed, special effect, floating text and group variables are destroyed:
call RemoveLocation
call RemoveRect
call DestroyGroup
call DestroyForce
call [...]
Curo is right; Players are internally constants, and so they do not leak (and cannot be removed with making the player leave the game ;P).
However, in your rect/region scenario, you do not need to remove the rect. Pre-placed Regions/Rects do not leak, as they are reused. The only time RemoveRect is needed, is when you create a region/rect by converting points, or some similar method.
I do know this - xenforo dropped the ball by not keeping the vbulletin reputation comments as a feature. The loss of the Reputation comments data when we switched to Xenforo really was the death knell for the site when it came to all the users that left. I know I missed it so much and I got way less interested in the site when that feature was gone and I run the site.
I'm on a page about incorrect corrections, and spent the better part of like two hours trying to get someone to understand that -5^2 = -25, not 25, and then that post had comments get reposted because that group is self sustaining, and that person was in turn trying to explain what I just explained to them. And I'm taking that as a victory