Roblox now offers official support for this via the Social Media Link feature! Developers will be able to include up to three social media links in their experience descriptions, similar to the method used in a user profile. Each type of social media can only be added once. These are the social media links that can be added to the experiences:
A Discord Server List such as Discord Street is a place where you can advertise your server and browse servers promoted by relevance, quality, member count, and more. How do I join a Discord server?
Using Discord Street you can browse through thousands of servers, search, and filter by tags. Discord Street uses a proprietary algorithm to deliver you the best Discord Servers that you're likely to be interested in. What is a Discord Server List?
Roblox blocked the word “Discord” in an attempt to prevent users from sharing links, but as you can tell it doesn't help.
Roblox doesn't want kids getting involved in a site that is for 13+ users. This will solve your problem discord is a filtered word on roblox and if you put a gui with the word discord you will get some sort of moderation for bypassing the filter.
The reason why Roblox censors just about everything is because it is a game meant for a younger audience. Gaming companies can't legally market their game to children unless it meets the content requirements to do so.
Roblox does not allow players to type numbers in chat. If they do, the number gets hashtagged, and players are left frustrated. The particular reason why Roblox does not allow numbers is to prevent players under 13 from sending their addresses and phone numbers in chat.