Pressing the Category button (under "page Settings") in RTL wikis do not open the "single category form" (like it does on enwiki), so one can't remove the category (one can still add new categories through "page settings", though).
the problem is not specific to hewiki or arwiki, but rather to "uselang=he" or "uselang=ar".
- open [[en:Ido Pariente]]
- press "edit"
- add "&uselang=he" to the address line and press <Enter> (should get you here: https://en.wikipedia.org/w/index.php?title=Ido_Pariente&veaction=edit&uselang=he )
- click the cog next to "הגדרות עמוד" (this is "page settings" in hebrew)
- click on one of the category buttons
WHAT YOU EXPECT
the category form should open. the form contains the little trashcan that lets you remove the category.
(try it without "&uselang=he" to see the form)
WHAT ACTUALLY HAPPENS
TESTED WITH BROWSERS
chrome and ff.