Hi, my friend RaymondSusanto from id.wiki reported this bug to me today. First he noticed that the interwiki he entered two days previously wasn't showing on this page
https://en.wikipedia.org/wiki/Category:Moscow_Metro_stations
Then I went to that page, and I reported that I can see the interwiki link to "Bahasa Indonesia"
https://id.wikipedia.org/wiki/Kategori:Stasiun_Metro_Moskwa
But he insisted that in his computer he couldn't see it. Then I tried in logged-out mode, lo-and-behold, the link dissapeared. I tried with another account (my bot), and I still can see the link while logged in. Raymond, on the other hand, couldn't see the link whether logged-in or logged-out.
I'm not sure how long it would be until the link would be displayed for all, because I haven't found any other case like that (usually I didn't pay attention to interwiki lag, but in ContentTranslation, apparently it is a needed feature - for automatching categories), so quicky take a look at it and report your finding here.