I think the end result of this is the importance of colour coding. Not sure if it's possible considering many of us are already using chat colour mods, but if OOC text could just be the same colour as tells which are always OOC per the rules, that would be great. Only issue is, the default bright green text of tells is not fitting for a chat channel that should be used sparingly and not so attention grabbing, so I guess you'd have to change both. A dim green or blue colour might be nice for that, on account of being cool, thus not so attention grabbing.
Dunno how viable it is to change all this on a server level, but along the same lines, I'd like to see colour coding for emotes being the same colour as DM channel text (orange for me, I think it's yellow by default), or the yellow text in the combat log for monster/DM emotes. Both of these being warm colours makes them more attention grabbing which is ideal since IC chat should be immediately noticeable.
tl;dr edit:
Cool colours are less attention grabbing. This suits OOC chat, like //, ((, or Tells.
Warm colours are more attention grabbing. This suits IC chat, like *, [, or DM text.
I know not all DM text is IC but when it isn't, it's announcements which typically pertain to everyone, so attention grabbing is justified.
I also gave them a small black dropshadow since the game does that too.
The background is the most common background on the server: neutral grass/dirt colours with a slightly darker tint, about the same tint as the default chatbox.
Not saying to change the colour of dialogue but this could help distinguish emotes from normal text if this is taken further. A colour coded chatbox is an easy to read chatbox and that helps when lots of people are talking.
Maybe this will help with adjustments if the system is kept.