I'm sure I just haven't found the right keywords to search with yet, but if I specify a copyright both in the project properties and as a command marker in the project, nothing shows up in the Windows-Properties: Details: Copyright info for the output MP4, regardless of whether the Main Concept or Sony encoder is used.

I'm expecting these markers to go into a private stream in the MP4 file, and to be readable by Vegas when opening the rendered MP4 - but they don't seem to be there.