allow using non-mentionable roles in some positions #79
Description
It would be nice to be able to use roles like everyone in positions that are not "summative" -- meaning, you can use roles you would not normally have permission to ping as the right-hand-side of any - or & operation. You would not be able to use it as the left hand side of an expression or the right hand side of a + operation.
This is nice because in these cases you'd be using the role to augment an existing role, and when used in those contexts it does not add any extra users to the output, which is nice.