Points
How points work
Points are a record of what you actually did. Everything below pays once, so nobody can climb the board by repeating themselves.
Two boards, two jobs
Inside a community the board runs for the month and then resets, so a member who joins today is never racing somebody a year ahead of them. Your all-time total keeps building on your profile and never resets, which is what the board on the home page is counting.
Why the caps exist
A lesson, a module and an assignment each pay once and then never again, so they cannot be farmed. Replies are the one thing a member can repeat at will, which is why they have a ceiling: without it, somebody writing a hundred throwaway replies would outrank somebody who finished the whole path.
Why likes have no ceiling
Each person can only pay you once for the same reply, so collecting a hundred likes means a hundred different people - and every one of them is a paying member. Buying your way up would cost more than it is worth. The point is also tied to the like itself: take the like back and the point goes with it, so the score counts the likes standing right now, not the ones that ever happened.
Tutors do not score
A tutor earns nothing in the community they run. They set the work, so a board they could win would not be a board. Everywhere else they are treated exactly like any other member: join somebody else's community and they earn on the same rules as everyone in it.