Hi, to me any more sounds as "never" in this case and any longer sounds like "not now or for a period of time" remember the meaning might change a little depending on the context, bye for now, I hope this helps Tony.

I think the difference is if we mustn't talk anymore, we mustn't talk at all. If we mustn't talk any longer, we'd better stop talking for some period of time.

Hi Danyel, They are quite similar, however "we mustn't talk anymore" is more final, suggesting conversation should be stopped indefinitely, whereas "we mustn't talk any longer" suggests the conversation has already continued for too much time. I hope this helps, Triss