To be clear appropriate usagesinclude:

• $wmgUseRelatedArticles is valid as there is no global $wgUseRelatedArticles.
• $wmgUseRelatedArticles and $wmgRelatedArticlesShowInSidebar;are valid as their values change depend on $wmgUseRelatedArticles

Anything that doesn't depend on the value of something else can be shifted to drop the m
It's highly possible in doing this task we discover all use cases are valid.

Sure. We have a lot of technical debt though and not all debt is equal :) fwiw i was hoping to look into this next week anyway. I have a lot of swats to do...

Current usages that I see:
'wmgUsePopups'
'wmgPopupsBetaFeature'
'wmgMobileFrontend'
wmgEnableTextExtracts
wmgExtractsRemoveClasses
wmgExtractsExtendOpenSearchXml
'wmgZeroBanner
'wmgZeroPortal
wmgMFEditorOptions
wmgUseRelatedArticles
'wmgRelatedArticlesShowInSidebar
wmgRelatedArticlesShowInFooter
wmgRelatedArticlesFooterWhitelistedSkins
wmgUseQuickSurveys
wmgUseWikidataPageBanner

Assuming that appropriate usage is only for things that are not actually config variables (unless noted otherwise) this narrows the audit considerably.

'wmgPopupsBetaFeature' - Looking at that list PopupsBetaFeature depends on the value of UseBetaFeatures so is appropriately used.
wmgExtractsRemoveClasses - looks like this can be removed as dates back to TextExtracts pre-extension loading
wmgExtractsExtendOpenSearchXml - simple boolean. No reason to use wmg
wmgMFEditorOptions - redunant this is true by default
'wmgRelatedArticlesShowInSidebar and wmgRelatedArticlesShowInFooter depend on each other so this makes sense
wmgRelatedArticlesFooterWhitelistedSkins - exists due to T142663

What do you think @Dereckson ?

Change 351922 had a related patch set uploaded (by Jdlrobson; owner: Jdlrobson):
[operations/mediawiki-config@master] Clean up inappropriate usages of wmg

https://gerrit.wikimedia.org/r/351922

@Jdlrobson - not sure why this is in needs analysis. Could you comment?

always read the comments...
https://phabricator.wikimedia.org/T151891#3236606
I'm waiting for some feedback from @Dereckson

Change 351922 merged by jenkins-bot:
[operations/mediawiki-config@master] Clean up inappropriate usages of wmg

https://gerrit.wikimedia.org/r/351922

Mentioned in SAL (#wikimedia-operations) [2017-05-10T13:34:41Z] <hashar@tin> Synchronized wmf-config/CommonSettings.php: Clean up inappropriate usages of wmg - T151891 (duration: 00m 42s)

Mentioned in SAL (#wikimedia-operations) [2017-05-10T13:35:42Z] <hashar@tin> Synchronized wmf-config/InitialiseSettings.php: Clean up inappropriate usages of wmg - T151891 (duration: 00m 42s)