It would simplify the api and consumption there of if all parameters that accept multiple items used a common delimiter.
We have semicolon and space that I know of so far.
Eliminating space as a delimiter is not necessary, but adding semicolon as a valid delimiter would serve to provide a consistent api and should not break existing code as semicolon is not typically a search component.
Also, regardless of whether there is a change, declaration of the delimiter on 'list of' params would be helpful.