Who asked whom about the cape of parchment? And who answered?

Question

I quote this cautionary tale about the dangers of studying Scholastic logic in full because it's just too good not to, but my question is only about the part in bold face:

Parisius accidit, quod quidam discipulus post mortem magistro suo de die apparuit, qui indutus videbatur cappa ex pergameno, minutis litteris conscripta. Cumque magister Sella, sic enim magister vocabatur, a discipulo quereret, quid cappa illa et littere sibi vellent, respondit: "quelibet harum litterarum magis me gravat pondere suo, quam si turrem hujus ecclesiæ super collum portarem," ostensa sibi ecclesia Sancta Germani Parisiensis, in cujus prato discipulus ejus apparuit illi. "Hec," inquit, "littere sunt sophysmata et curiositates, in quibus dies meos consumpsi," et addidit: "Non possem tibi exprimere, quanto ardore crucior sub hac cappa, sed per unam guttam sudoris aliquo modo possem tibi ostendere." Cumque magister extenderet palmam, ut sudoris exciperet guttam, perforata est manus ejus a fervente gutta velut acutissima sagitta. Mox ille magister scolas logice reliquit et ad ordinem Cystertiensium se transferens ait:

  Linquo "coax" ranis, "cra" corvis, vanaque vanis;
  ad logicam pergo, que mortis non timet "ergo".

From a discipulo, it appears to me that the student asked Sella what the cape and its letters meant to him (Sella?), and Sella responded with the story about how the letters weigh more heavily on him than if he were carrying the church tower on his neck. From context, though, that's obviously wrong: obviously Sella asked the student why the student is wearing the cape, and the student answered with his tale of woe.

On the other hand, quæreret is active, and maybe I'm misunderstanding vellent. How does the grammar clearly indicate who asked whom, and who answered? How can you tell who is the subject of respondit?

Answer 1

TKR has it exactly right:

Cumque magister Sella, sic enim magister vocabatur, a discipulo quereret, quid cappa illa et littere sibi vellent, respondit....

Translation:

And when Master Sella (that was the master's name) asked of the student, what the cape and letters meant, he [the student] responded....

Two idioms are used here:

• quaerere a(b) aliquo: means "to ask of someone" or "question." See meaning II.B.3 of L&S s.v. quaero. You could just as easily say ex or de.
• sibi velle means "to mean." See I.E.1.d or I.E.4. My Latin professor would say, "quid sibi vult X?" = "what does X mean?"