I wonder too. I was berated on here for mentioning that I deleted my reddit comments when I quit reddit, as if I was somehow stealing (my own content) from the users. Just weird IMO.
Well, as a Reddit user i dislike these "delete old comments" scripts since i very often read old discussions about topics i find interesting and when i hit the occasional "deleted by script foo, do it yourself too because reddit evil" i get irritated since they make following that old discussion hard.
It is your account of course, but i still dislike the practice since it goes counter to the entire purpose of a discussion site.
Only a small subset of users would be interested in those sites, and they likely don't come up in searches nearly as much as the original reddit post, so there's much more value to the deletion scripts than you are giving credit for.
A difference in the content of the two platforms doesn't mean that the comments on the two sites are so dissimilar that they can't be compared.
In particular, they remove the forum requirement of quoting the comment you're replying to, by allowing you to respond to someone's comment directly below it in the middle of an existing thread. It would be exactly as inconvenient to readers of old Reddit and HN threads if that context was deleted automatically 6 months after the fact, HN just doesn't let you do it.
> doesn't mean that the comments on the two sites are so dissimilar that they can't be compared.
Actually, it does. I discuss things of significance here, where the information may be useful to someone in the future, but I only commented on reddit for entertainment purposes (jokes, witty remarks, etc.) Also, creepy people don't comb through past HN comments looking to call you out in current conversations like they frequently do on reddit, and almost always out of context and spun to fit their agenda. While entertaining, it started getting annoying after a while, so in my opinion, that's why they can't have nice things, so to speak.
It is your account of course, but i still dislike the practice since it goes counter to the entire purpose of a discussion site.