...only if javascript is enabled.

I investigated this issue, on clicking 'watch' $.load() is executed which tries to rebuild the command menu by retrieving from the server.. This is wrong and we should be able to build it on client side without interacting with the server.

The actual error happens because the 'Change Subject' button is not build in PHP but in JS which doesn't appear using load()

https://gerrit.wikimedia.org/r/#/c/51834/

Patch depends on patch for bug 45329, hence adding dependency.

Change 51834 merged by jenkins-bot:
Watching and Unwatching made 'Change Subject' disappear.

https://gerrit.wikimedia.org/r/51834