It looks like when a mesh with old capture data attributes meet new skeleton with appended joints in a capture weight paint node, it might get confused and get weights on incorrect joints on various points.

Suppose I have a rigged character with simple body skeleton,
when I add detailed facial skeleton to its rest skeleton with a skeleton node, and then try to use a capture weight paint node to paint facial skin with modified skeleton node.
It will causing one of the facial joints automatically gaining weights at strange parts like arms, elbows, hips, belly.
Do I have to repaint the whole thing?
And even if I reduce weights of the facial joints on those strange skin regions, and when I reselect the goofy facial joints, weights on those off-facial areas suddenly reappears?

Okay, so you have a character and now you want to add facial joints to the skeleton and set up the capture weights for the new face joints?

If that is the case, It might be better to capture the face joints and paint the weights on a separate mesh (you can completely isolate the head for this) and use a "attrib composite" to add the new face weights to the original capture using a mask.