OK, this is most likely “caused” by my recent fixes to particles Edit Mode. The problem is, that fixed some root failures that were in partedit mode probably since BMesh was merged in - mismatch between indices of tessellated faces, and indices of polygons. Interesting to note that:

• This only affects children hairs.
• Freeing edit and re-creating the comb makes it perfectly OK.
• 'Cutting' all parents hair in partedit mode still leaves some stray children!

Think this demonstrates that those artefacts are caused by children laying around beyond their actual parent - in other words, this is not fixable, and I would really not bother about it. I’m sorry, but particles in general, and partedit in particular, are way beyond that kind of issues currently, so rule of thumb: if you have some edited hair working with one version, stick to this version or accept potential issues when switching to another one. :|