So, I've been seeing Bold Green Text used in place of the bold red text by some of the Mods. Is there a reason for this split?

If someone's using Bold Green Text instead of Bold Red Text, it's probably because the situation doesn't warrant the latter. As you can see, the red version is rather sore on the eyes, and serves as 'shouting'. Sometimes, we just bold the text. There aren't any major changes in philosophy behind this sort of shift, so you needn't read too much into it. Things proceed as usual.