This is about the old (traditional) Watchlist / RecentChanges pages.
The values for each "Show"/"Hide" link in recent changes / watchlist options box should be localizable per the show/hide state.
Quoting Pikne from bug 58449 comment 7:
Hm, I'm probably late with my comment, but in Estonian we need to decline
the noun differently depending on whether it is preceded by "hide" or
"show". So more favourable solution would have been to include the noun also
in these new per item messages.
Additional comments here:
[[:translatewiki:Thread:Translating talk:MediaWiki/Split some show/hide messages?]]