For the standard user the gadgets are just a collection of extra settings. He doesn't / shouldn't bother if its a MediaWiki core feature or a user script (while user script is only half correct since it's still enabled by admin / sysops though). The user instead needs to ask himself whatthe heck Gadgets are and why they are not logically sorted under the other sections but srted into h2 sections on the page (see Wikipedia).
MediaWiki:Gadgets-definition should be able to let you list gadgets into the standard sections or create new sections for it.
E.g. "Make text fields (e.g. the edit form) use a sans-serif font instead of a monospace font." would be better placed in the "Editing" section. Just my feelings. Example set-up of the Gadgets-definition:
== Editing == * wikEd|wikEd.js * textareasansserif|textareasansserif.css == Interface == * exlinks|exlinks.js * purgeTab|purgeTab.js == Misc == == library-gadgets == * JSL|JSL.js
The checkboxes for wikEd and textareasansserif would be added at the end of the Editing section
Interface would be a new section at the end (but before the standard Misc imo) including the stated two Gadgets.
At the end of the standard Misc section a new h2 would be added with JSL below.
If no "section" was defined in the Gadgets-definition, create "Gadgets" as is handled atm.
Makes sense to me ;)