Piestar:
Why would I ever post as more than one person? I totally frown on meta-gaming, and would never think I could speak for another character.
RPing two people in the same post does not automatically equal metagaming. There are plenty of games where someone roleplays their character and NPCs that they are in control of within the background of that character. Best example: a noble lord and his valet
There is also the thing of GMs posting as multiple NPCs in the same post, and again, not everyone is proficient in novel level writing. Correct punctuation and grammar does not equal good or easy-to-understand writing.
Just because you don't like the coloration, it doesn't mean that people are using it for bad reasons. It is a matter of preference, and for some people it is simply a matter of easier to read. The same reason why some people prefer to read books in ebook format, because they can adjust the contrast and color or increase the font to make it easier for them to read.
Also, not all people run the same color theme on RPOL either. Some have a dark theme, some have a light theme, the color tags change based on that as well.