The CDDB data is frequently wrong, or at least with minor errors. And misuse/abuse of the Compilation flag is a biggie.
I always review the metadata on a CD before I click the import button.
As for what should be done if a track’s Artist field features a guest? The solution is the “Album Artist” field. Set it to the primary artist for all tracks on the album. This will override the Artist field for the purpose of album grouping and it will sort with that artist instead of with the rest of the compilations.
But don’t use Album Artist for only some tracks on a single album. If some use it and some don’t, the two groups of tracks will be treated as separate albums. Similarly, don’t use both Album Artist and the compilation checkbox on a single album - that will almost certainly not result in what you want.
But don’t ever expect public databases like Gracenote/CDDB to get this right. It’s all crowdsourced data and a large percentage of contributors don’t understand what these fields are supposed to be. Always review and fix the metadata before you rip the disc.
You can submit your metadata to CDDB after making your fixes. But it won’t change the current data. It will simply (if accepted) add yours to the database, so future people will see two (or more) sets of metadata for the CD.