Tragedy and comedy are but two aspects of what is real, and whether we see the tragic or the humorous is a matter of perspective.

- Arnold Beisser, Author

In the instance you described above, and if I read it right, it sounds like the person with PPS was using his tragedy to provide humour to the person with BPD. Having BPD myself, I thought the joke quite funny, but it was perceived in a way that lightens the burdens of tragedies that both of these individuals deal with.

But as we can see by the responses, not everyone's perception is in sync (or timed well). Y'all might find this joke funny tomorrow...