Re: bp_xprofile_data remains even after user account is deleted.
Don’t worry too much about submitting tickets (and they don’t have to provide a solution) if you have a fair idea that something is of the nature of a bug – as you had hear – and can describe the nature of it as technically as possible with steps to reproduce if required then a ticket will definitely be reviewed and dealt with in one fashion or another. The Trac application is geared to tracking and logging and is far easier to find items when submitted to it than entering on the support forum where they may get lost, although it doesn’t hurt to start a forum post as well with perhaps a link to the ticket for reference.
Trac also may be used for adding ‘Enhancement’ type tickets so if you had a idea of an improvement that might be made or feature added that is the place to raise it as well.