Ok, I looked in specs (after such a long time). There what it says:
If multiple stereotypes are applied to an element, it is possible to show this by enclosing each stereotype name within a pair of guillemets and listing them after each other.
This means that
you should specify multiple stereotypes on one class as follows:
<<StatelessSessionBean>>
<< SessionFacade>>
However, specs also say that
A tool can choose whether it will display stereotypes or not.
So, it is normal that your tool does not display multiple stereotypes.
I found another example in specs that presents multiple stereotypes separated by comma, so your assumption was correct. As I understand, in your case you can use the following notation:
<<StatelessSessionBean, SessionFacade >>
which should be also correct.
Janis
SCEA 5.0, SCBCD 5.0, SCWCD 1.4, SCJP 5.0
OMG-Certified UML Professional, Intermediate; OMG-Certified UML Professional, Fundamental