Browser Support • Re: History/Forget About This Site: Intended scope?

IMHO, it's pretty logical, and I'd say it is by design. Think about it this way: forum.palemoon.org is a subdomain of [www.]palemoon.org. Any action on the base domain should apply to any of its subdomains, but not the other way.

This behavior can be useful for those sites that use subdomains for each of their categories, instead of firs level directories/path elements. If it didn't work this way, managing those multiple subdomain sites would be a game of whack-a-mole.