Actually my post could be divided in 2…
I did not enable any inline edit yet… and wonder on usability of the feature…
I enabled it in my test environment which is 7.8.8 and once I edit a field I get some-kind of “undefined” link instead of the check-mark once I clicked on the check mark…
So is this feature problematic or useful for your users?
That undefined is just a problem that needs solving in your system, for some reason. I don’t see it here. You can try the online demos to check that.
Try the permissions check as suggested above, or some JS rebuilds from Admin / Repair.
I love that feature, it’s a click-saver, very useful especially in list views!