I confess that I was disagreeing with the people that make those comments. It can go this way:
Someone says (in P&P board) that Charlotte didnīt believe Wickham story. Then someone else would say that she believed him, and brings that passage for evidence. ("JA says that Jane was the only person who defended Darcy, so that would mean that all the rest of people didnīt, and that included Charlotte").
My problem with this is that if we use the wording of this passage to conclude that Charlotte believed Wickham, then we must use it to conclude that she thought Darcy disagreeable. In conclusion, we don't know what she thought about Wickham. story.