Account per player is just when you have one login, usually something generic (so my login might be Liss) and you usually put links to each of your character's profiles in your sig or have an icon for each character in your sig.
Then when you RP and you want to use different characters you can either do subsequent posts, or you can split up your post from one character to the next. Like:
"this is talking," said Selwyn. "This is some more talking."
This is Selwyn's highly prejudiced opinion of the person he's speaking to. This is some more opinion. This is speculation about their psychological state and whether they're compensating for something.
"This is some more talking."
This is a description. This is more description. And this is description too.
______________________________
"This is scorn," said Ethel. "Everyone knows about this completely implausible theory."
This is an infodump. This is gratuitous description of Ethel's home life, including a mention of her pet alpaca.
"This is more conspiracy theory," Ethel went on. "This is far too much in depth explanation."
This is a passing description of what's going on around them.
"This is Ethel trying to get the last word," she said triumphantly.
by 
