[Aeran]

The problem is that MUDs are simply not interesting to many people anymore. What value is it to have an article in an encyclopedia about some MUD X? Very little to most people outside the MUD community.

To have an article about the MUD field itself is probably more interesting to a wider audience though, and such article should reach notability because it is mentioned in many independent .

Edit: It is pretty weird in a way. If you look at the entry for MXP it probably isn't seen as notable, because the only reference come from the subject itself. To get it notable someone would have to write a book/article referencing it, which means that author would read about MXP on the official website anyway.