Although my question is kind of a "display" thing (I specifically want to remove the display of this thing on this one page). I was looking for a server-side option. I don't think just hiding it in CSS is a very elegant solution. Wasted server effort generating HTML, and wasted browser effort receiving it all and then hiding some of it. Also the count of entries returned on the recent changes page will be wrong if we do this.
I'm surprised there isn't a setting to do this, because I think at some point MediaWiki was changed to start showing user creations here. So I always assumed there would be an option to go back if you preferred the old way. Guess not (or at least not without disabling the whole log)
"enhanced changes" is an interesting point because I see that the clutter is less of a problem anyway if you switch this on. The new user creations get nicely collapsed into a single line. So although that's not actually what anyone was suggesting... maybe that is the solution I'll go for ($wgDefaultUserOptions['usenewrc'] = 1;)
Thanks