On the "Edit User Settings" page (in the menu when you click on your username in the top right), there are "Notifications for Comments on My Posts" and "Notifications For Replies to My Comments" checkboxes—one would hope that, as long as those are checked, the bell should give you notifications when people reply?
On the old site (like on Reddit), there was an envelope in the upper right that led to all replies I'd received to my posts and comments. Now there's a bell; but all its tabs currently say "You don't have any notifications yet!". What am I missing?