I know that some apps and browser extensions do this, but I really think that it’s important for Lemmy itself to have an existing notes feature as part of the server software and backend, which allows your notes to be saved as part of your account.

Mastodon has this feature and lets you leave notes on users’ profiles. I do this a lot on there. I guess there isn’t any reason why you couldn’t use Mastodon’s version of it if you regularly post to Lemmy communities from Mastodon, but since I and many others are lemmy users, and post + read from here it’s good to have that feature available on this server’s software natively.