Starting from p/4997637 it has been discussed why nicknames are not legit "guest names" for Guest mappers. Since it's not written in the rules despite being ab absolute pointless thing - because this has nothing to do with creativity and freedom - an addition for this should be done.
Guest Mapper should use their username in their Guest Difficulties. This means that the creator of the guest difficulty use their recent username to ensure that they provided the content. Abbreviations can be used in an appropriate amount and should be handled case-by-case.There is no reason to use an unrelated name - which is only known in a small circle - for a guest difficulty if you can use your username instead. We also cannot exactly know if that's actually true or just an excuse to use a random name just for the running gag/meme's sake. That's not how it should ever works. The Easy Difficulty in this mapset used the name of an existing osu!user - which can implies that they actually made the difficulty.