I haven’t seen a statement from Anet but from what I’ve seen in practice if it’s not an exploit they don’t mind.
Some of those places have been accessible since launch and well documented (like getting down below Rata Sum) and they haven’t stopped people getting there or (as far as I know) banned anyone for going there.
Danielle Aurorel, Dear Dragon We Got Your Cookies [Nom], Desolation (EU).
“Life’s a journey, not a destination.”