The problem that I have with BKT, and in general the taxable bond CEF universe, is the dismal dividend record. BKT has a long 20-year history of dividend cuts.
Their inception dividend payment was $0.0917. They now pay a paltry $0.024. In their entire history they have raised the dividend only once while cutting it nine times, per etfconnect.com stats.
The 1.78% in "other expenses" is too high for a fund with a 4.9% yield. I don't follow BKT and have not read their shareholder reports, but my guess is that their employment of leverage has not been effective and is costing the shareholders too much now.
Just my opinion of course.
Best,
Steve