I pulled my Leslie off the shelf and looked this up on page 314 and the endnote for the incident on page 475. Leslie's note about this and related things of page 314 cites Union reports and the Kansas City newspaper, neither of which would be solid primary evidence about Taylor's alleged second wounding in his good arm.
However, Leslie also cites Taylor's own letter dated 4 May 1879 to Kansas historian W. W. Scott as held by Kansas Collection, University of Kansas Libraries, University of Kansas at Lawrence. I have not seen this letter, and I do not know what it contains. That being said, IF Taylor in this letter told Scott that he was wounded later accidentally by his own men and this convinced him to give up his military career, then Taylor's own account would be strong primary evidence to me. I just hadn't heard of this before.
Postwar, Fletch Taylor enjoyed telling about his war exploits, particularly after he grew wealthy from his lead mines in Jasper County and serving on the Missouri General Assembly. By that time the southern Democrats were back in power and southerners openly spoke of the concept of "the Lost Cause." It was in vogue to interview Confederate veterans in Missouri once more, especially ones as colorful as Fletch Taylor.