I understand your dilemma: if the semicolon went before the 'however', one would use both 'however' and 'but' to mean the same thing.
The issue, in my humble view, is that the original sentence has a precarious logical construction, in how it connects the flow of ideas: putting a "however" just before a "but" obfuscates the meaning, because it piles two levels of opposition in the same place (perhaps the writer was in a hurry).
'However' creates an opposition between the first clause ('Characters... to each other') and something written before the paragraph (which we don't see here).
'but' creates an opposition between the second clause ('there is a differentiation... characters') and the first one.
If one really wanted to improve this sentence, why not going further and fix the order of ideas? At this point, editing would be required. There might be various ways, but one could try this:
However, characters in the novels are not always morally and socially
obliging to each other, but there is differentiation between the
upstanding hero or heroine and the socially less acceptable
characters.
Here we would break the (non-absolute) rule that 'however' should never be at the beginning of a sentence. Hypothesis: did the problem originate from a rote application of that rule?
So, if the word 'however' was the problem, let's try to flesh out the meaning:
It is true that characters in the novels are not always morally and socially
obliging to each other; yet there is differentiation between the
upstanding hero or heroine and the socially less acceptable
characters.
(Here I followed the suggestion of putting a semicolon and changed the 'but' into a 'yet', to make it crispier.)
But to check whether that was the best flow of ideas, one would need to see the previous paragraph. Furthermore, we are in the realm of composition, which is open of opinion. What I wished to illustrate here was a method of resolution, rather than a pat answer.
however
assuming that the sentence preceding this one carries the thought being contradicted. I would then put a comma after thebut
, giving it the meaning ofhowever
, and adding a further contradiction to the contradiction. – Thomas Jay Rush Sep 26 '17 at 23:55