The change was made because a lot of people told me "the problem with filtering" and "the reason we can't behave ourselves and want to move to another site" is specifically that if they hit the number link on Favorites showing the number of new posts written, and the first of those posts was from someone they had filtered, they were seeing it.
The only way to address this was to change the routine that does one-at-a-time message reading. Specifically, if it tries to land on a post that is filtered out either because it was written by a filtered person, or it was written *to* a filtered person and you've got that extra level enabled, it'll pull up the next non-filtered post on that board.
So now if you've got filtering enabled, there're fewer ways to see their posts. If you've got people filtered, they're filtered. If you don't, they're not. No more of the "Well, they're filtered unless such and such happens".
Filtering is pretty absolute now. Either the posts are filtered out or they're not.
Personally, when I'm testing filtering and therefore need to toggle it on and off quickly and easily, I keep a separate window open on the My Filters page.
I suppose one solution would be to add yet another "level" of filtering that would allow you to see "filtered" posts either because they're the next one up when you're on Favorites or because someone gave you a link to them, or because they were written to you and appear in your MailBox, but I'm not willing to implement that. The levels of filter-testing and the number of unique queries they require are already at the maximum level of complexity and server workload I'm willing to live with.
Would making the toggling of filters a lot easier solve the problem? I'm thinking along the lines of a new button right below the top menu, that would change back and forth between "Filters On" and "Filters Off".