I came across a website that implemented the option to leave a note or comment in a way I had not seen before. It's a rather cool alternative to sending them a mail or submitting a message via a form.
I had to
ssh firstname.lastname@example.org*, and when the connection was established, it asked for the note and some optional personal information.
Note: Oh, this is a great idea!
Name (optional): Mészáros Róbert
URL (optional): https://www.implenton.com/
Once I submitted the information, there was a thank you message, and the SSH connection was terminated.
Since it was a developer-oriented website, typing something in the terminal for the reader might be even simpler than all other options.
*I won't share the actual domain here because it was posted on a Gemini capsule. That would be a branch of "confidentiality". It's up to your imagination or for you to implement it.