Fluorescence is an additional identifying feature for a diamond. It is almost never noticeable even if it’s “strong”. Fluorescence is the visible light some diamonds emit when they are exposed to invisible ultraviolet (UV) rays.
What impact does fluorescence have on the appearance of a diamond?
GIA studies show that, for most diamonds, the strength of fluorescence has no widely noticeable effect on appearance. In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence. In the mid-color diamond range, fluorescence may actually help improve the color appearance.
A diamond that fluoresces has the same integrity as one with no reaction to UV. Nothing in either instance inherently weakens or is bad for the diamond. There is no sound reason for avoiding fluorescence. Yet, if the diamond is larger or the price is lower, you benefit.