The difference between expectation and guideline is the guidelines will be enforced, and expectations are just things we suggest for more fair play here but will not be strictly enforced. ^^
People may notice that in the collab corner, there are more than one collab opened on the same song. This is wonderful because more people have a chance at joining and collabing ^^
What I want to suggest is that if you have already joined a collab on a song and another collab is opened on that same song, please try to resist from joining it unless they are in real need of joiners so that more people can have a shot at collabing.
Especially in the Korean collab corner, if you've already joined a collab on the same song, let's give others a try shall we?^^