I have a hard time thinking how it would work. For example your comment posted at https://discuss.tchncs.de/comment/5907612 posted at "Sunday, December 24th, 2023 at 8:40:09 AM GMT+00:00". If you back up and restore to a new account in 6 months, does your new account get to retroactively repost this comment to December 2023? What about top posts you make?

Individual emails make sense as lone documents but on social media the individual items are only comprehensible in context.

If you just want a record of your individual posts/comments without context you can point an RSS reader at the feed available on your home instance user page. (Lemmy users only; for some reason this feature not available to kbin.)