Submitted to Minecraft's offical bug tracker, they're saying it's a mod-related issue. Could it be caused by the individual mods?
Link to issue: https://mojang.atlassian.net/browse/MC-2595
Hi,
Now I'm not sure if this is a issue in Forge or with Minecraft itself, but whenever the text is supposed to display the thousands separator it shows a "NBSP"-character instead. (See attached image)
http://cl.ly/image/2L3p1s0M3X0h
I suppose this is because Java automatically formats it to my region settings.