Source of the post There shouldn't be any limitation for that. It's just discouraged to have several posts in a row in the same thread.
Makes sense. But I got that error message when I tried to post here just after having posted in the science news thread. I waited a minute and tried again, and then the post went through. Not a big issue, but somebody might want to look into this if it's not intended that way.
Nice. But you can easily remove the remaining noise. For instance, try experimenting with selective gaussian blur in Gimp. Use a low threshold in the center, and a higher threshold for the remaining area.