In another comment, the original poster mentioned that the keyboard shortcut to close a tab isn't cmd+w, because they don't want users to think about them as "tabs" and don't want to think about "closing" them, they're trying to organize things as items in a TODO list.
The value that this provides then, isn't in actual features. All of these features can at least be mimicked in other browsers, either natively in Vivaldi's case, or with extensions and OS features. This browser's value would be in streamlined usability and new way of thinking about organizing things. For that reason, Hacker News in general isn't really the target market. Power-users don't want a new way of thinking about browsing or a streamlined experience, they want the customizability of Vivaldi.
I think the marketing here needs to re-framed from focusing on "faster at your work," comparisons to vim, and extolling the virtues of keyboard shortcuts. The people that are interested in that are using Vivaldi or Vieb (https://vieb.dev) or have their own Firefox setup configured just right. You should focus on providing an opinionated way to organize and simplify browsing, letting the browser handle tab management. Reminders for tabs I think is a good idea that no other browser is doing. But can I make reminders for arbitrary text content? A 'browser with keyboard shortcuts' has been done before. A 'browser that is also a TODO list' is more interesting.
Just my 2 cents.