It seems as though Darth Vader sees the loss of limbs as a rite of passage. Having lost nearly all of his own limbs thanks to his duels with Count Dooku and Obi-Wan Kenobi, Vader thinks that the lessons learned through the experiences were so valuable that he sought to "teach" it to others after the events of Revenge of the Sith, while also foreshadowing significant intention behind his duel with his son Luke Skywalker years later in The Empire Strikes Back.
During Charles Soule's Darth Vader comic series for Marvel Comics, the Dark Lord's earliest days as a Sith post-Revenge of the Sith are revealed, and a handful of issues show his first interactions with the Imperial Inquisitors, the fallen Jedi who aided him in his hunt for Jedi survivors who survived the purge of Order 66. Once they were put under his command by the Emperor, Vader sought to hone their abilities in the dark side of the Force, seeing them as weak as they still relied on the defensive tactics they'd been taught by the Jedi Order. This eventually leads Vader to teach the Inquisitors one of the most important lessons of all in 2017's Darth Vader #7 from Soule and artist Giuseppe Camuncoli.
Remarkably, the issue begins with the Sixth Brother kneeling in pain before Darth Vader, whose crimson lightsaber is still activated after having cut off the Inquisitor's arm. However, Vader acts as if the hacked-off limb is simply a mere inconvenience and distraction to be ignored, commanding the Sixth Brother to get up and keep fighting. While the Grand Inquisitor voices his protests and questions Vader about what maiming the Inquisitor could possibly teach him, Vader enlightens him: "Loss."
Not only that, but Vader then adds that none of them will forget the feelings of loss as the issue reveals that the Sith lord cut off a limb from every agent of the Inquistorius (not just Sixth Brother). In Vader's mind, the pain of loss is the primary source of his power in the dark side, using it to stoke his feelings of rage, hate, and suffering which are all foundational and necessary elements for wielding the dark side effectively. Furthermore, this also provides a hint as to the reasons why Vader cut off Luke's hand in Empire Strikes Back, as Vader likely wanted to give his son the most valuable lesson he could about the dark side, wanting to motivate Luke to turn to the dark and join him to overthrow the Emperor. Unfortunately, it seems as though losing limbs is the best method Vader knows.
However, Luke proved to have a stronger resilience, resisting the dark and resolving to continue his Jedi training on into Return of the Jedi and beyond after redeeming his father back to the light. However, the fact that Darth Vader seemingly had some prior intention and reasoning behind cutting off his son's hand is a rather interesting facet of the Star Wars timeline, rather than it being just a random casualty of their lightsaber duel on Cloud City.