How to remove the left-hand blue line on custom selected styled Listbox items?

Answer 1

Have a look at this answer to a similar question. Basically, if you want to restyle the ListBox so that selected items have a different background colour, it's easier to simply change the "HighlightBrush" colour so that the selected item uses the colour you want.

Answer 2

I'm pretty sure this is a bug, as several people have had this issue with the ListBoxItem template.

To fix, just add:

<Setter Property="Padding" Value="0,0,0,0"/>

to your ContainerStyle template. It's originally 2,0,0,0.