The Impossibility of Double Gallows

[DONJCH]

Hi ChenZheChina,
Anton and WladimirD both mentioned these unusual small gallows over You are not allowed to view links. Register or Login to view..
There appear to be two of these small gallow characters in the Voynich, the z character and the double-loop one you mention, but both are extremely rare.
I don't know what to make of them.
I wonder if they might be mistakes, or result from extreme abbreviation, or hint towards words borrowed from another language than the rest of the text, or if they are just very rare characters in the plaintext language. Or...?

Some say the first one (tis) is quite common. others say these unusual ones are all rare and probably errors.
Without actual figures or a benchmark definition for rarity, it is impossible to judge.