@ovasileva and others: Please see https://en.wikivoyage.org/wiki/Wikivoyage:Travellers%27_pub#Change_of_Mobile_View_Watchlist for a potentially urgent problem that's likely related to this.

Related to this, do we need to add a check for "too few"? There are many pages at the English Wikipedia that have 30+ "watchers" (so the number gets shown) but a single-digit number of watchers who are active editors. Is it possible that someone could see "on 50 watchlists, but zero active editors are actually available"?

In T355914#9537231, @ovasileva wrote:

Another step in the process here would be to look at how the change would visually affect current layouts on enwiki and across wikis...

Right. It's a mess, the numbers need to be changed, and nobody will want to be responsible, e.g., for "taking away" the 320px and substituting the more immediately useful 300px, or for changing the prefs settings from 300px to 320px. That will require, at minimum, a series of meetings. A plausible temporary "fix" would be to run a one-time job that pregens a 250px (and probably 300px) copy of every image that's currently used, and then switch the wiki(s). After that, the images can all be processed at human scale, when they're added to the articles.

In re https://phabricator.wikimedia.org/T355914#9505896:

Same song, second verse. This hasn't worked for weeks.

@Guy_Macon, did you ever post those numbers?

A problem in the Modern skin has been reported: https://en.wikipedia.org/wiki/Wikipedia:Village_pump_%28technical%29#Notification_look_change