Khemaka is otherwise unknown.

Dāsaka has a verse at Thag 1.17.

They were mistaken, as will be made clear later. Even a stream-enterer does not regard the aggregates as self, in the sense that they cannot form a view to that effect.

The key difference here is between “I am” (asmi), the intuitive sense of being someone, and “I am that” (ayamahamasmi), the identification of that someone with something in particular, namely the aggregates (see MN 47:13.4 and note). | Read avigataṁ per SN 22.47:2.1.

The reason for the extended back and forth is not exactly clear. Perhaps the senior monks initially sent a messenger so as to not overburden the sick monk with many visitors, and got caught up in an unintended discussion.

Prefer vaṇṭa (“stalk”) over vaṇṇa (“color”), though both are possible.