This is interesting because I have never considered this line might be read referring just to Meryton. I learn something different every day! (:D) Here is my thinking.

In that respect his friend had greatly the advantage. Bingley was sure of being liked wherever he appeared, Darcy was continually giving offence. (Ch. 4)

Bingley’s likeability and Darcy offensiveness (above) seems historical to me because they are attached to descriptions of them and their friendship. A “steady friendship” suggests it is not a new one and Darcy “never appeared dissatisfied” with his temper compared with Bingley’s suggest an opinion held for quite a while. The word “wherever” seems suggestive of many events. Bingley returned Mr. Bennet’s visit (3) and I assume did right by all other attentive gentlemen as well but as there is no revealing gossip of dinners out or shooting with so and etc. it seems either nothing happened or there was a shocking failure in the Meryton gossip mill. The word “continually” to me paints a picture of Darcy offending over a longer period of time than one evening and one event—his first social appearance in Meryton is at the assembly? The next paragraph shifts to the present with their thoughts about local society as observed at the assembly; if Bingley’s likeability and Darcy’s offensiveness refers only to Meryton it would fit well at this point.

I see Kathleen’s point about merit but I don’t see “being liked” and “continually giving offence” as they are used meaning one hundred percent of folks at any given event. Bingley is a person that tries to be agreeable and obliging to all he meets so being generally liked wherever he appears does not seem unreasonable to me. I grant if it was someone else then it probably would seem terribly unreasonable but Bingley seems to be fashioned specifically to be liked with his warm, “lively and unreserved” (3) manners and the “easiness, openness, and ductility of his temper” (4) that is endearing to many—even Darcy. Like Sir William he is “all attention to everybody” (5) and although he is not the host of the assembly Bingley tries to do “a very gallant thing” by his friend and a distressed lady just as Sir William does in Ch. 6. Bingley is rather more sensible and much less impressed with rank than Sir William which is yet another attractive quality.