I imagine that whoever looks at implementing this will consider all the options, including tags/categories.

The behaviour where emails stop if the page is not visited while logged-in is the current design, see T33928 (it is also mentioned in the notification emails themselves). As mentioned in this task, the current implementation may have bug(s) or subtelties, particularly regarding minor and bot edits.

Regarding '...your mailbox will be flooded with thousands of mails...' comment above, perhaps the emails could be tagged for easy sorting in popular email clients? (Outlook has 'Categories' which can be added to emails to help with sorting). Maybe a system could be devised so that all emails relating to one page can easily be searched-for using tags.

I agree this feature would be optional.

Adding the page to my Watchlist and setting email notifications to on does not provide this functionality - the emails stop if I don't log-in and view the page.

I would argue that these last two suggestions also do not satisfy this task:

Regarding your question 'which specific and non-theoretical problem does this proposal try to solve?', this would probably fall more into the category of a new feature rather than solving a specific problem.

Neither of the links you provided satisfy the request for this task:

scfc, as requested, I have filed a new request for mail-for-all-changes, T114587. The RSS feed won't do what I want, in a simple way, as far as I know.

This wouldn't help confirm or debug the particular problem I experienced.

To cover some points from people's comments:

We need something that works, is transparent and easy to use.

Thanks for your very clear response.

I guess there is the possibility that I visited the page itself while logged-in (without looking at the history or differences), and re-enabled emails without realising it. Is that possibile?