Many people are that oblivious. There are tons of questions in the #help category without answers to the questions presented when creating a new topic, so a little nagging is in order. It may be a little overboard sometimes, with that I somewhat agree.
How do I disable the “your topic is similar” modal in new topic. It covers the post preview and it popping up grabs my attention in a rude and noisy way while i’m in the middle of trying to type out a train of thought.
I am not sure that the forum software allows you to do so directly.
I would suggest asking the user not to message you anymore. If a user persists in messaging you afterward, you can flag the user’s private messages as inappropriate and a forum administrator may get involved.
Note that forum administrators may still message you about flags, warnings, and complaints, including complaints you make about other people or complaints other people make about you.
I hope another forum administrator can correct me if I’m mistaken.
In private message threads, there is an exclamation mark icon which lets you control how often you are notified about a topic, and you can set that to “muted”. But I’m not sure that affects subsequent topics sent by the same user.
… in your user preferences on the site, there is a section for Notifications, and you can add individual users to a “Muted” list there so that you don’t receive notifications from them.
Edit: in that section you can also turn off certain other kinds of site notifications, and you can also add particular topic categories to “Muted”.
I’ve merged your other topics into this one since they were all more or less questions and feedback regarding the forum software.
Most of your questions have been answered now. Some of the things you mentioned - like the on-boarding process, or the “similar topic” feature - cannot easily be disabled or are there for good reasons and dramatically reduce the number of duplicate questions that get asked here.
That being said, if you have specific suggestions for UX improvements for this software (Discourse), I would suggestion posting those over on the Discourse Meta discussion forum.