AtoU page 60-61 border: this reads as a deprecation without a deprecation

[wrwilliams]

Advice to Users: The use of a global shared buffer can be problematic when used for communication in different libraries, as the buffer represents a shared resource used for all buffered mode communication. Further, with the introduction of the Sessions Model, the use of a single shared buffer violates the concept of resource isolation that is intended with MPI Sessions. It is therefore recommended, especially for libraries and programs using the Sessions Model, to use only communicator-specific or session- specific buffers. (End of advice to users.)