As noted in original response, it does look like a rapier, or more likely small sword/epee blade. Given the very purpose of pirates, to plunder vessels typically European engaged in East Indies trade, the captains often wore small swords of the fashion of the period. As these were known as a mark of authority, which would have been perceived as such, and understandable that a pirate captain, such as Zheng Yi Sao might have posed with such a sword in the manner depicted, if such illustration in period might have been possible.
The fencing glove would have been far fetched as in the period suggested the manner of fencing using this sort of equipment was not yet formalized in any notable degree.
The premise of the discussion has thus become IMO the validity of the illustration as far as accuracy in presuming the type of weapon used by this important pirate figure. While the thin blade illustrated seems as noted a court sword type, the hilt with folding guard (seemingly) is of key notice.
At this point, the course of discussion is primarily what is known as 'historical detection' which is evaluating recorded accounts, iconographic art etc. forensically, and what sources actually were depicted. It has been for me one of the most fascinating areas in studying weapons from these perspectives, and it is great to see others sharing in these views and ideas,.
I regret that Pirate Lady seems to have left as it would have been interesting to know more on what perspectives are involved in her project. Still an intriguing topic.
