If no hsdis library is found, the instruction length is treated as 4 on x86. That results in output like this:

   0x000001902854702c: f03b d0fd
 ;; B12: # out( B22 B13 ) <- in( B11 ) Freq: 0.35821
  0x0000019028547030: 488b d541

There is logic to check for code comments within a range of bytes (see nmethod::has_code_comment), but for block comments, we only seem to check for an exact match of the beginning offset. That means we can miss block comments.