Can I delete my Lemmy account and just vanish?

Even if you managed to delete the posts from all federated servers, they will still be archived in various places like the wayback machine and similar.

Better to only post what you're comfortable sharing forever.

No.

If you post it on the internet, it's there forever.

It's interesting that this is kicking up some controversy. Personally I've held similar thoughts since the time of AOL, that once it leaves your system it's no longer in your control. You can ask people to delete it, and maybe they did, or maybe they deleted the one copy but not the cache version, or maybe just didn't and lied about it. I've actually accidentally found stuff I thought was long lost when I decided to just mess around with some data recovery tools and pulled a bunch of pictures back from a drive I didn't remember them ever being on.

One of my kids I saw take a picture of a snapchat with another phone. Asked what they where doing and it was explained that if you do a regular screenshot it notified the other person, so this was how they kept a copy secretly. So with that in mind, you never know who has copies of what that was posted.
- It’s interesting that this is kicking up some controversy.
  
  Yeah. You'd think that people on the fediverse, protocols that lend themselves to mass-scraping, would understand that it's out of their hands once they post it.
If this were really true, why is there the existence of link rot and a large volume of online lost media?

I think the proper way to say this is that “if you post it on the internet, you should consider it being there forever”.

For example - a personal one. I did a short ambient music podcast series highlighting artists who release music via Creative Commons (a new thing at the time). It was only 5 episodes, and I have the first one archived. The other four are now completely lost to time, despite being put out on the internet back then. It’s not there forever.

In terms of social media, it’s harder to not be forever, but even that’s down to the same issues - has someone else archived it, screenshotted, especially in the case of a site ceasing to function? Internet Archive doesn’t preserve everything either. Plenty of archived pages missing images or files that enable true functionality to view everything as it was.
- I’ll bet someone has copies of those 4 episodes. I know I have random things downloaded and stored (mostly music and Git repos) that are no longer discoverable on the internet. You just need to find the right data hoarder.
  
  And I guess that’s part of what is meant by if you post it on the internet it’s there forever all it means is you never know who has a backup
- I'm gonna archive this post and back it up twice so future generations can witness your immense pedantry.
- Lmfao, I had this showerthought not too long ago: https://sh.itjust.works/post/37145912
  
  😁
That maxim is no longer true, especially in the medium-to-long term. Reddit posts older than 8 or so years old aren't accessible (even to their creators), same with the original Digg posts. If you go back to the Usenet days, most posts haven't been archived and are lost, especially those from the smaller newsgroups. I expect over the coming decades, we'll see data loss as a growing issue.
- I can see my first reddit posts from 2009 on wayback machine.
- Its probably in a government database somewhere, it's only inaccessible to you.
  
  Reminds me of this joke (with a modern digital-era spin):
  
  The son is accused of drug trafficking
  
  The father: "I can't access the cloud drive account on [Site Name]"
  
  The son: "If you ever remember the password and get in, delete the account. That's where my (drug trade) ledger is"
  
  Overnight, the FBI filed subpoena to the cloud company requesting a copy of any files on any of [the father]'s accounts. Within days, the company compiled and send the info to the FBI.
  
  [The son]'s defence attorney got a copy of the files due to the discovery process, and passed it on to the father.
  
  The father: "Son, I don't know how, but your lawyer just sent me an email this afternoon with all the family photos"
  
  (Original Thread: https://sh.itjust.works/post/37145912/18347741)

If you used Tor or a Reputable No-Log VPN, just check the "delete all posts and comments" and delete your account. You should be safe.
If not, then ask your instance admin to delete logs of your IP and then delete your account along with all posts and comments. If they follow through, you should be safe.
If you don't use Tor or VPN, and your admin refuses, or lies to you about deleting the IP, then you have no recourse but to go to settings, check the box, and delete your account, and hope your adversaries don't gain the cooperation of your instance admin (e.g. Legal Orders to obtain information).

Edit: The info isn't gonna be completely gone, but if you didn't post any personal identifiable information, it's just a random stranger's post on the internet, not attributed to you.

It's pretty easy to do in your Lemmy account settings. For someone who has done this many, many times .

with that said, while you can delete your content from the physical server any screen share, or internet archive are kept forever, also this might not clear your posts from federated servers.