I now know the answer to the question ‘who needs a system of sigla?’
A: Piers Ploughman scholars. Lawrence, who cares (possibly too much…1) about manuscript sigla, told us on tuesday that there around fifty MSS of Piers. And a single MS could have several sigla, refering to the texts within (so, for example, an MS with both C and B recensions in it will have two conventional sigla- one for the C and one for the B text.) This is all very confusing, but, on the other hand, with so many MSS, if you tried reffering to them by manuscript short title, your word count would disappear quicker than you could say ‘verbose’.
On the other hand: Piers Ploughman scholars have sets of conventional sigla! I am very jealous.
1. Just kidding, Lawrence. One can never care too much about persnickety details, I say.