To add to the other security conscious comments, even if you wanted to run a VM, there are attacks that escalpe the VM and hit the underlining OS

Computers are inherently insecure

If you are a human posting, you’re contributing to the community. It shouldn’t matter if it’s your only or have X accounts that you use/don’t use. In general, ddos attacks are more timing related in combination with data quantity not just raw data, since a new user account doesn’t take up much space and neither does their posts (this isn’t 100% the case, but usually the case. Also haven’t read lemmy’s source code, just general discussion)