If you inactivate your account (in your settings) your username gets replaced with user-inactivated. If you want the content of your posts deleted, you'll have to delete them. We don't have bulk deletion as of yet.
Bulk deletion is always sad as it breaks the historical record of conversations and devalues everyone else's contributions through decontextualisation. But I guess it's the choice of the deleter. We don't have bulk deletion as of yet.
If you care enough you can always go back and edit comments. Reddit allows comments to be edited to be empty no matter the age, which is an odd oversight/quirk on their part. I occasionally go back to old reddit comments and remove them all - usually because I feel it is something I am not comfortable with saying or having traced to me that has to do with my personal life at the time I wrote it. I wouldn't do so on Hubski: it is the anonymous nature of Reddit that appealed to me with those posts. I love my friends here but it is because I am known and know them that I sometimes am reticent in sharing now. Also, doxxin' and shit.
To inactivate sounds like a reversible process. What if I want to delete it for good? I mean the account, not necessarily the content.