I recently noticed this "Clear all filters" in my flagging history option.
I'm guessing it should be fine clearing all filters once in a while?
"Clear all filters" is just a display option. It has no persistent effect.
If you click on any of the flag categories like spam flags
or post flags > declined
, you set a filter on what flags are displayed in the current view. This is reflected in the browser URL too, e.g. https://askubuntu.com/users/flag-summary/current?group=2&status=2 gives you all helpful (status=2) spam flags (group=2).
The "Clear all filters" link only brings you back to the main flag overview with no filters applied, i.e. https://askubuntu.com/users/flag-summary/current