realign procedural comment with code it refers to
Prevent 'Unknown Var' popup when reporting improper UserPref settings
'Delete' changebar marker assigned to wrong text window
simplify logic of 3way merge pre-assignment
fix 'unknow Var' fault in Prefs dialog when different Engine cmds exist (circular-ref issue)
incomplete prior edit caused occasionally missed text window repaints
repair cmdline parsing to restore ancestor .vs. arbitrary arg pass-thru syntax recognition
clarify commentary, minor code simplifications