Can you activate a planeswalker's loyalty ability multiple times in one turn?

A planeswalker's loyalty abilities are governed by CR 606.3: you may activate a loyalty ability only once per turn. This is a special rule unique to loyalty abilities — it is not a cost restriction but a hard limit baked into the rules themselves, regardless of how many loyalty counters the planeswalker has.

Additionally, CR 606.3b requires that you activate a loyalty ability only during your main phase and only when the stack is empty (i.e., during your priority window at sorcery speed). You cannot activate them in response to spells or abilities, and you cannot activate more than one loyalty ability on the same planeswalker in a turn even if it is a different ability.

Note that the once-per-turn restriction applies per planeswalker object. If you somehow control two separate copies of the same planeswalker (which is normally impossible due to the legendary rule, but could happen in edge cases), each copy has its own once-per-turn limit.

Example: You control Chandra, Torch of Defiance with 4 loyalty counters. You activate her +1 ability during your main phase. You cannot then activate her −3 ability later that same turn — you have already used your one loyalty activation for that planeswalker this turn.