Aeroglaze 306 is used extensively as a thermal control coating on spacecraft components. It's a nice high emissivity flat black that has a lot of heritage on both internal and external parts of the spacecraft. It has good handling properties (adhesion, light wear/scuff resistance, doesn't pick up a lot of volatiles from the atmosphere like moisture). While there is some weathering that might occur over time due to UV and atomic oxygen, the LDEF experiment LDEF Paper showed generally stable properties for this material.
As a high emissivity coating, it's excellent for radiating heat energy away from a part, or absorbing heat and solar energy. Often it's used as a radiating surface on the exterior to reject heat to deep space if that section is normally shadowed. Internally, it can be used to coat various boxes and surfaces to radiatively couple components together thereby evening out minimum and maximum temperatures.
Z306 has also been used to reduce light reflections on components that are adjacent to sensitive optics, but often the most sensitive optics need even higher performance and assurance that debris won't be generated. In these instances one used to rely on black anodization, but the new Vantablack coating may be a good candidate for these applications.
But, getting back to the referenced article, these coatings would only address part of the problem, removing specular reflections of sunlight from metallic portions of the spacecraft. In practice, white paint is a better thermal coating to use for this because it won't heat up as much in sunlight. Lord Industries also made A276 white paint for this purpose. A diffuse paint will not be bright enough to bother earth bound telescopes too badly, even if it's white. What really causes problems is the glint off the solar arrays. The cover glass in particular can create a very bright glint at certain angles. And of course, you can't paint that part black or you won't get any power. Anti-reflective coatings are a start, but they're not broad spectrum so they're not super effective. Other solutions like making the outer surface less smooth tend to cut into the power production as well since they scatter more of the incoming light instead of passing it through. So there may only be minor improvements that are possible without affecting performance.