What are the rules about posting links in fictions?

When I was first setting up my fiction on here, I noticed that it told me that links to discord servers and other sites were not allowed in story descriptions. I do desire to promote my discord server, as interactions with fans of my story is one of the key ways I improve it, so I'm wondering what the stipulations on this are.

I am wondering if I'm allowed to have links to my discord on every chapter, for example, like I do on scribblehub, but I'm not sure if this is allowed. On Wattpad where I don't have the link at the bottom of each chapter, I've noticed a number of people saying that they never noticed I had a discord until they looked at my bio one day.

So yeah, all I'm looking for is some clarification on the rules.