Reminds me of that old Dropbox "ShowHN" post.
Looking back at old emails takes some heart, I'm afraid of the idea as I'd probably cringe too hard.
My Reddit account just had it's "cakeday" which means I'm in the "9th year club" and the idea I have comments from 9 years ago still publicly available kind of scares me. Too the point where I feel motivated to write a script to delete anything beyond >1-2yrs back.
Old comments on HN I'm not so scared of as I tend to put more effort to only post competent/civil comments here. Plus you can't delete them even if you wanted to.
I'm going to take a contrarian view that this is not necessarily something that we need or want to keep associated with ourselves. There are groups like Archive Team and IPFS who talk about how ethereal components of the web cause vanishing history and a lost cultural heritage, while neglecting to note that the web is first-in-its-kind because it makes pedestrian, routine conversations to be transcribed and accessed from all over the world.
In olden times, even personal letters would generally include significant news or interesting updates, and these were never intended for a non-personal audience. The high cost of committing information to a fixed medium like paper, as opposed to the ethereal domain of air in which conversation naturally abides, would cause self-selection that made for only the elements considered most significant by the authors or artists to be committed. I am not convinced that archiving every comment or writing that gets published is a necessary or even beneficial part of preserving a cultural heritage. In some cases, like Geocities, the benefit is obvious, but I doubt the value of treating every conversation or exchange as a prized historical artifact.
There are several reddit auto- and back-deleters already. Check out shreddit [0], which I've used with some success in the past, and which can be configured to retain certain high value posts (posts above a user-specified score threshold or that have been awarded gold). I think it's good to keep this running on a continuing basis so that unless the comment is exceptional, only the last few months of comments are available.
This is particularly important/valuable if you have any slightly controversial opinions on anything. Over the years, it's easy to accidentally leak a little information here, a little there, and when a psycho decides to go on a vendetta against you because you insulted the species of grass they just installed in their front yard, it's too late to go back and plug those little leaks.