(I have moved your post from Community position statement, contribution guidelines, forum improvements to this - more appropriate - location)
On the forum we’ve had similar discussion a number of times in the past (e.g. “Why does this forum have Like buttons and Likes?”).
The answer is: We are an exemplar of Humane Tech practice, but we are also a ‘place of action’, a workplace, if you will. So, for instance, the Likes are there to show you agree, rather than posting an “I like that comment” and making the thread too long, didn’t read (TL;DR).
This notification thing is a bit different in that this type of notification is not strictly necessary, but it can be handy if you are involved in many discussions and tasks (I do not use it, but am very happy with the small notification icon in the top-right corner above my avatar that shows forum activity).
This feature stems from the Discourse software and built-in browser capabilities. I don’t think it can be disabled in forum settings. But you could ask a question about it in Forum Meta or file a feature request there. If there is such setting you can notify me, and we can consider changes (we are a crowdsourced community, and everyone is a volunteer, including me).
Note however - and also for others asking similar questions - this forum is not an exemplar of Time Well Spent (i.e. will not have grayscale UI, be rid of Likes, notify of time spent, etc.). But the community at large will be an exemplar of Humane Technology