How to tag IPLS with multiple people in the same role?

General Discussion
#1

When it's a person in two roles, I do it like this:
Role1:Person1;Role2:Person1;
It's wrong? It should be Role1, Role2:Person1; or another way?

And what would be ideal for the reverse case?
Role1:Person1, Person2;
Role1:Person1,Person2;
Role1:Person1/Person2;
Role1:Person1;Role1:Person2;

#2

See the documentation on the supported fields:

which says:
Notes Role1:Person1;Role2:Person2; … e.g., Drums:Jamie Graham;
To be safe I would allow 1 pair only. This would lead to repetitions.
But: what does your player support?