TLDR: If you use "hard refresh" in your browser after editing a CSS or JS page on the wiki, I'd like to hear about it so as to figure out whether there may be a bug in the software. Please do test and confirm it for yourself once more without a hard refresh, as it might just be an old habit acting as a placebo :)

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The "clearyourcache" message is the message that, contrary to its interface key, instructs users to perform a page refresh in order to see the effect of their edit to JS and CSS-related pages. For example:

https://translatewiki.net/wiki/MediaWiki:Clearyourcache/en
https://en.wikipedia.org/wiki/MediaWiki:Common.css
https://meta.wikimedia.org/wiki/MediaWiki:OSM.js
https://meta.wikimedia.org/wiki/User:Krinkle/global.js
https://en.wikipedia.org/wiki/MediaWiki:Citoid-template-type-map.json

As I understand it, this message is no longer be needed. I'm not aware of any scenario in which a page carries this message, and edits to the page in question would propagate to the editor's browser sooner as result of performing a "hard reload".

If you find yourself doing hard reloads, or know people that do, I'd love to hear detailed examples of specific combinations of pages/wikis/browsers where people do this.

I've detailed the technical reasons for why these (should) have no impact, on Phabricator:
https://phabricator.wikimedia.org/T291744

-- Timo