I brought this up last year, and got scolded for being an unsafe hunter. As with most questions, though, whether to wear blaze or not depends on various factors.
Where I hunt in Colorado, the cover is normally shorter than waist-high, and often only 18" -24" tall. In this type of cover, I guarantee you that birds see blaze very easily. Have proven it to multiple non-believers over the years. They get no shots, I get plenty. But, I digress (or is it me saying "I told you so!"?). In stubble and short grass, if someone is wearing blaze, and someone calls to, or whistles at, their dog, the birds are alerted, and look up. "I see you", and they run off, with us not knowing they were there. If you are silent, sans dog, you can get on top of birds before they flush.
I hunt without a dog most of my hunts, and we get 2 or 3 apiece most days (I hunt with a max of 4 hunters in the field). With dogs, the grass has to be deeper for us to see as many birds as I see (silently) without a dog.
I wear a vest with orange in the back, since they can't see around corners. This way, I can be seen from the side by my hunting partners (not that they can't see me in thigh-high grass), even if they are not really paying attention. I hunted for years with no blaze, with no problems. I encourage anyone who wants to go hunting with me to not wear orange on their front. It makes a huge difference in short cover.
In tall cover (chest-high or taller), I doubt that blaze hurts your success, since the birds are deep in the grass. But, if they fly, they will see your blaze and flare away, no question. If I go to SD to hunt, ever, I will have removable blaze for my head and front, so I can wear as-needed. But for the cover I hunt in Colorado, no blaze on the front for me.
