That's not so nice... Also because, seen from AFSDK, i don't really see a good reason why this should not be supported.
But to your questions:
- Limits are not references to other attributes (although you can configure them to be). It is just confusing that the path also includes the | symbol
- I think here the same applies, this is only the reference within the Formula sources itself
How i read it (no time to test) is that it is not supported to use an attribute reference in the PI Point DataReference. Maybe someone else can shed some more light in this?