Really sorry about this Tim! Comment positioning in canvas mode is janky at the moment, to be honest ther's quite a few parts that are janky positioning wise. i'm working on some foundational fixes for how pages are created/duplicated/deleted then I plan to work on positioning issues.

Really sorry for the frustration in the meantime, if you're getting more pain than gain from canvas mode you can disable it for now (all pages will be an old "version" in the top left).