I know for fact our server allows No-Clipping, because I could do it perfectly fine on World of Minecraft Client 1.8.1.  Then when I downloaded 1.8.6, it would no longer work. 

I cannot speak for versions 1.8.2 - 1.8.5, because I never downloaded them.  I WOULD just use 1.8.1 all the time...  But I REALLY enjoy the copy/paste text feature of 1.8.6 and up.  Someone screwed up the code or something on a version since 1.8.1 and it just keeps getting carried over into all the new versions.  PLEASE FIX THIS.  I'm an SOP on our server (Patrick Shwarz), and this feature really helps out.