To me, the most important thing with posts is that they got plenty of space, easy to read, follow a certain logical pattern in their structure.

Avoiding walls of text is the most important thing someone can do, in my opinion.

Maybe use italic to signal a whisper or that a person is thinking, like:

-
"Ohhh, I don't mind it at all!" Nela said, smiling back at Bob and nodding her head.

[i]"My, what a dummy."[/i]
- 

Normally I'm not a fan of people coloring their texts, but I can appreciate it if it's like in a fast forward conversation between two or more people, like:

[color=ed1c24]Nela[/color]
[color=0054a6]Ali[/color]
[color=ec008c]Tim[/color]

[color=ed1c24]"NO, I swear I didn't steal the loot."[/color]
[color=0072bc]"Shut up, you were the last person in the room!"[/color]
[color=ec008c]"Guuys, can we please just calm down? It's no reason to get angry... "[/color]
[color=0072bc]"I'M NOT ANGRY! I'M FURIOUS!"[/color]
[color=ed1c24]"Uhhh, I'll just go out the back!"[/color]
[color=0072bc][b]"COME BACK HERE!"[/b][/color]