Why not just emend the text, use the consonantal
text, and be done with it?
Or, go with the versions. At Qumran, Isaiah A has BWMTW,
his altar? singular anyway. The Greek has
tou thanatou autou, singular. The Vulgate has
sepulchrum suum, singular.
I don't think the plural needs to be read here.
Liz
A2