This app looks very nice, and I love markdown. But I am not prepared to pay £8+ per month for a Markdown notes app that works on all my devices, especially if it exerts control over what I can do with my own files. I can sync my Markdown directory via Dropbox, iCloud, Nextcloud, etc and edit the files with things like Obsidian, 1Writer, VSCode or any one of hundreds of Markdown editors.
If you'd like to sync it yourself, then by all means do so. I don't necessarily understand comments like these, if the user doesn't like it, no one is forcing them to buy it, especially if there are other solutions as you've stated.
> I don't necessarily understand comments like these
It's called constructive criticism. The application dev is reading this forum, and will be able to see what people like and dislike about the app and the business.