All the time I edited my post it always shows like this but sometimes when I edit earlier or within a few minutes it doesn't show at all.
I can also see the changes when I login with a PC it doesn't even show at all untill I hover around the post then it comes up as the first user said.
Yes. Edits are not recorded within the first ten minutes that the post was made, I think this is to give the user a short window to make any quick edits that they want to.
It was originally 5 minutes, but was later changed to 10 minutes. I think I remember theymos making a post or reply about that, but I can't find it now.
Edits aren't recorded when they occur within 5 minutes of the post time. (This has always been the case.)