Question about paragraph justification

[nablator]

I wonder if this is unusual or a common irregularity from before conventions were established?

It there were any good parallels, common or uncommon, someone would have found them by now. There are, on occasion, end-of-line inserts above or below the line (to save space) and, very frequently, catchwords at the bottom of the page, both in mss. and printed books. Chapter endings in a V shape, with lines becoming progressively shorter until the last word, became fashionable in printed books but I don't remember seeing any in 14th or 15th century manuscripts. Catchwords and cute chapter endings are not really comparable to the right-justified and centered lines in the VMs anyway.