Community Rules:https://forums.elderscrollsonline.com/en/discussion/502831/community-rules

I suspect this part applies.

Advertising: We do not allow advertising on our forums. This includes, but is not limited to advertisements and promotions for the following:

• Outside businesses and services
• Other games
• Any venture that results in monetary profit

We do not consider the promotion of guilds, fan sites, and fan groups, or the activities and content thereof, to be advertising. Please feel free to let The Elder Scrolls Online community know all about your guild, fan site, or fan group! Simply keep in mind that you may not promote your guild, fan site, or fan group if you are looking to turn a monetary profit by doing so.

If you'd like clarification, ZOS_Kevin is a fairly active Community Mod who might be able to answer you better.