Yep, most related to the GitHub - discourse/discourse-spoiler-alert: A plugin for discourse to hide spoilers behind the spoiler-alert jQuery plugin plugin is currently missing Finnish translations. You @Silvanus are familiar with the following topic but for others, see:
I said “most” because the Blur Spoiler part I translated. Yeah, did something wrong, but @zogstrip fixed it so it is now seen here in Meta for instance.
So I translated Blur Spoiler to Spoileri already. I always seek for ways to express things in pure Finnish instead of anglicisms, but here I made an exception. Words like spoilata (to spoil smth) and spoileri (spoiler) are very common expressions especially among young people these days, and I can’t imagine a proper synonym for them.
Which leads me to my point: you shouldn’t translate Hide Details to Spoileri because the expression is reserved for the other functionality. The exact translation would be Piilota yksityiskohdat indeed and it is a long phrase. However, it should work: I think that it fits where it is supposed to fit, as Listauksissa näkyminen fits, too. About neater options, Yhteenveto (Summary) can be quite misleading. Perhaps Piilotettu teksti (Hidden text) could work?
By the way, did you check if the modification you did to Hide Details actually took place? I just tested it at Nettitelkku.com and nothing happens. It still says Hide Details. There probably is some good explanation for this behavior.
PS. I re-translated the term Arvomerkki to Ansiomerkki in the weekend.