Requested in https://www.mediawiki.org/wiki/MediaWiki_Stakeholders%27_Group/TechConf_Input/Challenges#stronger_warnings_when_trying_to_edit_old_version
> Our documentation process makes heavy use of the recent changes feature. Due to the breakdown by day, there is no easy way to only list a page's most recent edit, it will be listed for each day it was edited. This means that if I am away for a week, and then start reviewing changes from 7 days ago, I will likely look at a few diffs that have had additional changes since. [see T10681 for this issue] It is easy to start editing the version that is not the current one, which is not usually what is intended. I make the mistake even though I am aware of it, and it is almost impossible to explain to less technical users that this is something to watch out for. This leads to later edits being clobbered, which is reducing buy-in in using the wiki.
> **It would be nice if trying to edit a non-current version led to a far more "noisy" warning than that little line at the top. This might be something that I can change through interface edits, but I think the default should be more noisy in the first place.** [emphasis added]
Codepoint: https://gerrit.wikimedia.org/g/mediawiki/core/+/master/includes/EditPage.php#3095
Wrap in either `warningbox` or `mw-warning` CSS class. See [[https://www.mediawiki.org/w/index.php?title=User:Quiddity_(WMF)/sandbox&oldid=2860082|Demo of both those]]. Probably `warningbox` unless there's guidance somewhere (I can't [[https://www.mediawiki.org/w/index.php?search=warningbox+-prefix%3AMediaWiki&title=Special:Search&profile=advanced&fulltext=1&advancedSearch-current=%7B%22namespaces%22%3A%5B12%2C100%2C102%2C104%2C106%2C0%2C4%2C8%2C9%2C10%2C11%2C107%2C13%2C101%2C103%2C105%2C14%2C2300%2C2302%2C828%2C829%2C90%2C91%2C92%2C93%5D%7D&ns12=1&ns100=1&ns102=1&ns104=1&ns106=1&ns0=1&ns4=1&ns8=1&ns9=1&ns10=1&ns11=1&ns107=1&ns13=1&ns101=1&ns103=1&ns105=1&ns14=1&ns2300=1&ns2302=1&ns828=1&ns829=1&ns90=1&ns91=1&ns92=1&ns93=1&searchToken=3atpotf099f00u2zikex1vfch|find]] docs for that).