HBD is unlike most convertible bonds in that: 1) there is no ability to hold it to maturity and receive payment in anything other than 'equity' (native HIVE token in this case), and 2) the conversion ratio is variable, not fixed. The latter is why convertible bonds can trade up or down depending on the stock price but HBD mostly won't.
When the haircut rule comes into play, the conversion ratio becomes somewhat fixed, and HBD may trade more like a traditional convertible bond, moving up and down along with the HIVE token price.