Please bring back the preference to turn off highlight as temporary selection

[micheus]

If I wanted to write a plugin (or hell, even a homebrew version if the plugin API isn't low-level enough for this) to turn highlight as temporary selection on and off, where should I look in the older versions' code to find how that toggle used to work?

You are wellcome to write Wigns3d plugins, but you don't need do one for this - you just need put back the code that was used before, test it and pull a request to dgud.
Here is the changes made by Richard Jones (a.k.a optgon) for clean up the preferences.