Probably copy/pasted path introduced something unprintable somehow?? Or it’s a bug in parsing the string?? The file contained strgui/font:^R4^? upon closing. The manually typed-in path worked fine, but not every time. Tried few times, results are mixed bag. Weird.
Me neiter 
Also, Ctrl+x does not stop vkdt properly, either. Well, not every time:
$❯ pgrep vkdt
13256
…truncating config.rc to 0 again.
I’m not sure which signal Compiz sends on Alt+F4, and can not look because it seems that if I start vkdt from a command line, it does not stop it properly at all, so echo $? gives 0 all the time. You don’t process SIGTERM/SIGHUP, do you?