I seem to run into the same issue time and time again with my lightweight knit gloves. The space between the thumb and forefinger ends up wearing and it starts the impending unraveling. I am just a baby textile repair-ist and instead of just guessing I wanted to bring it to others attention.
Is this a good candidate just for darning? Would a patch reinforcement be better? Call it quits and get another pair?
i'd say this looks like it is just unraveling and not suffering from heavy wear. I'd get a needle and thread (maybe embroidery floss weight) and reinforce it that way if it were mine.
these industrially knit gloves just sort of jump from one part of the glove to the other without the stuff we'd do when we knit by hand (weaving in, for example).
A patch would probably look super cool right there, but you'd want to find a fabric that is pliable enough to not make it feel bulky when you fold your thumb in.
If this is a repeat problem, that suggests to me that your hand and the glove aren't quite a match, so the seam is getting too much pressure. I'd vote opening the seam a little and making a knitted "gusset" that gives the area more material.