I would burn off the loose threads, problem is you will likely not get all of them and the fraying will begin again.
We have about 40 bcd`s and do a bit of this kind of repair. You could dribble a little bit of super glue just to keep the loose ends down, or
FYI
3m 5200 adhesive/sealant is an excellent product for any kind of BC repair.
It takes a week to set up, and gets all over the place.
With non bladder BCD`s we successfully repair cuts in the bcd with patches using the 5200, if you are careful you can put the patch on the inside of the bcd. overlap the cut an inch or so put some soap on the inside of the bcd behind the patch so the 5200 does not stick it together, Use some nylon bcd material, the 5200 sticks to the plastic liners and the nylon shell material. Cover with a thin plastic bag, also with soap on it, weight it, let it sit for a few days and if you did a good job, you will see just a fine line where the cut was. We have some repaired like this in service for 2 years, with no problems. Staff members have even used it to glue on inflator hoses attachments and opv valves that have cracked while waiting for new gear to arrive, one went three months with daily use before a new bcd got here, and was still going strong.