Per https://www.mediawiki.org/wiki/Talk:Reading/Web/Desktop_Improvements#Bug?_Footer_engulfes_content historically floats inside of user generated content have been cleared by skins (see also https://gerrit.wikimedia.org/r/c/mediawiki/skins/Vector/+/608976).
This should not be the responsibility of the skins to know, but should be a documented feature of ResourceLoaderSkinModule.
The new clear style would likely live in the existing `content` feature or a new `content-user-generated` feature and be inherited by all skins.
```
.mw-parser-output::after {
content: "";
display: block;
clear: both;
}
```
[x] Add the new rule
[] Make sure the rule is documented https://gerrit.wikimedia.org/r/c/mediawiki/core/+/674452
[] Make sure the skin is enabled by default for skins using the ResourceLoaderSkinModule opt-in policy https://gerrit.wikimedia.org/r/c/mediawiki/core/+/674452
[] Remove any redundant existing clear rules in Example Skin
[] Remove the redundant clearing rules in Vector https://gerrit.wikimedia.org/r/c/mediawiki/skins/Vector/+/673989
# Sign off
The following should be pulled out into separate tasks or fixed as part of this change
[] Remove the redundant clear:both on #footer for CologneBlue
[] Remove the redundant div.mw_clear element inside Modern
[] Remove the redundant .visualClear inside Monobook
[] Remove the redundant .visualClear inside Timeless
[] Opt-into the new feature and remove the redundant clear on #page-secondary-actions inside Minerva.