Ask HN: Dormant Hacker News accounts suddenly springing to life years later?

So I'm a long time lurker of HN and like to randomly inspect accounts/users to see the account's other comments and submissions. But one thing I noticed sometimes when I do that is I see the account (for example) was created FIVE YEARS AGO with two or three comments made five years ago, and a recent 2021 comment with long durations of time between each comment.

I imagine the accounts are lurker accounts where the person is signed in, refraining from commenting and then bringing some life into the account on a whim.

I'm not mentioning any accounts since I respect the privacy of those types of accounts, but with some digging you can spot them all over HN.

Also I've seen some accounts with no comments, with the account created 6/7 years ago and then suddenly a comment appears. Why do people do that? It's weird. Anyone else know this situation but haven't actually expressed it yet on HN?