There’s also sort by Top (with various time filters), Hot, Active, and Most/New Comments, all of which are very much algorithms. What it doesn’t have is sorting based on user activity, which also isn’t what’s coming in 0.19. What’s being added is basically the same as ‘Hot’, but takes into consideration the activity on the sub, so as to let smaller subs in a user’s feed not be drowned out by more active subs.