When reciting Psalm 81 on Thursdays, I'm always puzzled how can we decide whether the last letter ך of the psalm should get a dagesh or not. In the Aleppo Codex it is clearly written without dagesh:
Same in the Leningrad Codex:
I've noticed that Heidenheim didn't add it either (just like all other contemporary digital editions), yet ArtScroll and many other prayer books I had in my hand over the years had ָךּ in the word אשביעך. What determines whether we write the kaf of the second person singular suffix with a dagesh?