Hey @fdekerm! I’ve updated your post title to better fit our guidelines: How to post in the Questions category
Make sure the title is something you’d ask to a friend. 
If by comments you mean review comments in the web app, no, comments are not automatically deleted under any circumstances, even if you delete the code they point to. If that ever happens to you, please let us know as that would be a bug.
Of course, if you delete the code under a comment, the comment won’t be displayed at that position anymore since the code is gone. That does not mean the comment was deleted: it will still be listed in the “Improve” tab (the pencil icon to the left)!
If by comments you mean // Typst comments, those are only deleted if you delete them in your source code as well.
Let me know if you need further help!