Steps to reproduce:

1. Go to Admin -> Plugins -> Filters -> Manager filters
2. Change any one filter to 'Applies to' 'Content and headings'

Unexpected result: Your Moodle site gets about 33% slower.

Then spend a day profiling, etc. to discover that navigationlib.php is causing many calls to filter_get_active_in_context, I eventually found this setting in the code, which led me to MDL-67428, and the discovery that we were not alone in our pain.

I can see why, at the time when MDL-67428 was first implemented, it was prudent to default the setting to off.

However, it is now tried and tested, and pretty much essential to have this on if you are using 'Applies to' 'Content and headings', and it is irrelevant and does not harm if you are not.

So, I am making this issue to chagne the default for new Moodle sites.