I know that option - d is just for debug that is why I put it in brackets (just use it as default in case of unexpected behaviour to track the source).
The other point is where I get stuck. I had it enabled (as many others) too and wanted it too keep being enabled like running imscp-reconfigure has done. So the question is why imscp-installer cannot activate it when imscp-reconfigure can.
But at least a note in Errate file would be fine (as you wrote).