Not sure if it's a bug or intended. But even if the trade feature is globally disabled and the trade permissions for usergroups are set to NO, the alert options in user's Preference page still shows. Some options are shown as well even if a user has no permissions like the ones below.
Reacts to your item (Create items permission is set to No)
Reviews your item (Create items permission is set to No)
Creates an item in a watched category (Is there a watch/unwatch option for item categories, we dont see one)
We're receiving inquiries regarding trades and we have to respond awkwardly that trade is not available. Same with how to create an item.