From my experience, having just upgraded to v4, I notice that text highlighting doesn't work for me when editing custom code. What I mean by that is, if you click and drag to select text, you are selecting the text but you have no visual feedback that you've anything selected.
It could be a graphics driver related issue but as I'm using a bog standard Nvidia GeForce 980Ti with latest drivers.
By contrast, text highlighting works when editing CSS so I doubt it's a driver issue :)
You are correct, I still have the v2.7.1 32bit version as a back up that I can use if the 64bit version fails. In version 4, there is no highlight being displayed on selected Custom Code content. When I open up v2.7.1, the Custom Code component does have highlighting.
No problem, glad to help :) I notice today I have an update to 4.0.1 so I hope this resolves that issue. Thanks for the prompt reply and action, much appreciated!