Known Limitations

Activity Diagram

The name of the Interruptible Activity Region is not read.
The visibility of the Interruptible Activity Region is not read.

Sequence Diagram

Duration Observation is not read.
Time Observation is not read.

Eclipse environment with org.eclipse.uml2

Both solutions are registering to EMF their own implementation for handling .uml and .uml2 file extensions.
For avoiding conflicts, registration of com.sodius.mdw.metamodel.uml21 can be disabled by adding an environment variable:
com.sodius.mdw.metamodel.uml21.enableRegisterResourceFactories to "false"

This environment variable could be set inside eclipse.ini of the running product, after -vmargs field:
-vmargs
-Dcom.sodius.mdw.metamodel.uml21.enableRegisterResourceFactories=false

This would make org.eclipse.uml2 as default reader for .uml and .uml2 files.