I was modifying an email template and I noticed that when moving the cursor over a piece of code it changed.
Here is a screenshot from before:
Vim version is 7.4 on Ubuntu 16.04. Any idea what would make something like this happen?
Your terminal window isn't configured to display colors properly.
You can test whether this is the case by disabling color in vim and see if the problem goes away.
Disables color features in vim:
:syntax off :set nohlsearch :set t_Co=0
If this fixes it but you want color support, the next step I suggest is to check your terminal emulator and shell configuration for ANSI support.