I interpreted it as being about his personal dept that he must've accumulated by not paying himself a salary. Which, yes, is alarming if not irresponsible (but perhaps understandable, I haven't been in this situation).

Some investors insist on a personal bond, but yeah, that's obviously something you should avoid if at all possible.

Those are bad investors. For anyone raising money and reading this: if an investor asks for a personal bond, do not take money from that investor. That is either an investor behaving badly, or an investor who doesn't understand the risk of startups and should not be investing in them.