Good manners or not, it's a glaring inconsistency for Mr Wickham to say "I have no right to give my opinion" and then to spill the beans. Elizabeth, who's claimed to be diverted by "follies and nonsense, whims and inconsistencies" (ch11), laps it all up without so much as a quiet chuckle. She goes on to give Mr Wickham credit for having "truth in his looks" (ch17).

That's unlike the rigour she applies to Mr Darcy. For example, she quickly rejects Mr Bingley's information because it presumably all came from Mr Darcy, but doesn't pause to reflect that Mr Wickham's information is also just one man's word.

It may be dreadfully derogatory of an heroine's dignity, but she appears to have let herself be complimented and provoked out of clear thought, by the two men's different treatment of herself.