the privilege of exchanging any vacant evening of his own blank solitude for....

[Moonzero]

"Real, long-standing regard brought the Westons and Mr.Knightley; and by Mr. Elton, a young man living alone without liking it, the privilege of exchanging any vacant evening of his own blank solitude for the elegancies and society of Mr. Woodhouse’s drawing-room and the smiles of his lovely daughter, was in no danger of being thrown away."

Emma by Jane Austen chapter 3 volume 1

The subject of " was in no danger of being thrown away " is the "privilege", right? And if so, could the sentence be rearranged to ( the privilege of exchanging........., was in no danger of being thrown away " wasted" by Mr.Elton)?

 

[entangledbank]

Yes, Ignore the extra description of Mr Elton, and ignore the exact description of the privilege, and you have:

and by Mr. Elton [. . .], the privilege [of . . .], was in no danger of being thrown away.

Or, rearranging,

the privilege was in no danger of being thrown away by Mr Elton

That is, Mr Elton was not at all likely to throw away the privilege. Moving the agent 'by Mr Elton' to the front is unusual, probably even unusual in Jane Austen's time.