About [[MediaWiki:Watchlist-details]]
I don't think it's a good idea to turn the system messages into documentation. The wording is correct, because you can only watch a page (and its talk), and when you click "watch" on a talk you're still watching the page (and its talk). So what's confusing is perhaps the watch button on talks, and that tooltip (or the message appearing after clicking, now in a JavaScript box) could be improved?
The wording is correct but the situation is potentially confusing. It would be also ok if the feedback messages MediaWiki:Removedwatchtext/en, MediaWiki:Addedwatchtext/en will say that both, the page and the talk page are watched. The tooltip is MediaWiki:tooltip-ca-watch and MediaWiki:tooltip-ca-unwatch. I wonder if {{TALKPAGENAME}} and {{SUBJECTPAGENAME}} could be used for clarification.
Adding separately (proposal #2) to the message will not overload the message, won't be wrong and IMHO it would be also an improvement.
I'm closing this thread for now as it's inactive. If you still think it should be changed, please file a bug in MediaWiki>Watchlist so that hopefully someone else will weigh in.
Because Rillke felt boring and isn't annoyed by this system (this here for discussing changes) that is obviously not working, he opened bugzilla:53098 over such a stupid tiny issue.