I happened to be writing an entry and noticed that there was something odd about using the link definition name reduce. The preview updates fine until I enter the last e of reduce, then nothing changes. The editor just goes into pause mode until I remove the e again.
I'll submit this post with a test link using the link definition name reduce to see if it's just the preview that's not working properly: Test
Other, non-working names: map, filter, pop, push... yeah you get the idea? Any Array function.