What I'm saying is that you use to design on a color calibrated monitor that is matte. And I'm also talking about color bars /standards for video also...where color temperatures would not exceed a certain level. An example is the reds/yellows you see on say your computer/youtube for many things, etc would never be 'legal' for a television...those colors would have to be 'toned' down for NTSC viewing...but we don't design just for TV anymore and for a lot of things, television is becoming the minority viewing device...over mobile, tablets and so on. In fact, I'd reckon to say many new young video people don't even know about color bars if they've only been making web docs/web videos and so on.
With everything now going to mobile devices, youtube and so on, and with viewing being mainly done on glossy screens for the majority of these devices, the argument for AGAINST designing on a glossy monitor really doesn't hold much weight anymore...and some could argue that you should be moving TO a glossy display so you can have the same display as your target audience.
As far as I understand it, whether the monitor is glossy or not has nothing to do with the panel or its colour reproduction abilities. It's all about the panel and the electronics driving it. The glossy / non-glossy is just the coating on the cover over the panel. An aggressive anti-glare coating may impact the user's ability to see all of those colours, but not the monitor's ability to produce them.
Let's take a look at the Apple Thunderbolt Display and the Dell U2711. They are both using an LG panel and I believe it's actually the same panel, but obviously different electronics and also one is glossy and the other isn't.
LCD Colour Quality (Percent of AdobeRGB 1998) higher is better
Dell U2711 - 95.69
Apple Thunderbolt Display - 76.1
Colour Tracking - XR Pro and Xrite i1D2 - Uncalibrated Average Delta E (200 nits - lower is better)
Dell U2711 - 2.24
ATD - 7.62
The ATD is pretty bad in comparison to its competitors out of the factory.
Colour Tracking - XR Pro and Xrite i1D2 - Calibrated Average Delta E (200 nits - lower is better)
Dell U2711 - 1.06
ATD - 1.63
The calibrated results are a lot closer, but the Dell is still better
By the way, the 30" ACD was even better when calibrated
ACD 30" Calibrated - 0.91
But it could only display 72.96% of AdobeRGB 1998
Now, I am no expert, but it seems to me that the non-glossy Dell is better at colour accuracy when measured using scientific and objective means.