After a great deal of debate, I've decided to bring this topic up in its own thread. I'm not sure how to go about this without pissing people off because such a huge number of Pens writers are guilty of this, myself included until a wonderful writer reviewed some of my work and pointed it out to me.
I'm talking about, for lack of a better term on my part, generic descriptors. The blonde, the redhead, the hacker, the Wiccan, the witch, the Watcher, the Slayer, the ex-vengence demon, the petite blonde, the construction worker, the (insert any job here), and on and on...
Why are these bad? It is a signal that we, the writer/narrator are coming through too much in the story. I'm not Hunter Thompson. I don't want the reader thinking about me. I want them thinking about Willow and Tara. I want them swimming around in their heads and hearts and feeling their emotions. Using a generic throws up a barrier that our reader doesn't want or need.
How so? Tara doesn't think of herself as "the blonde". Willow doesn't think of her that way either. She's Tara. She's her everything. By putting up that barrier, we force our reader to step back and see our characters for one or two traits only instead of as a whole, well-rounded, three dimensional person. Buffy may be the Slayer, but she isn't just the Slayer. We can display a character in their entirety by using their names. If I say "Tara" to a group of Kittens, I'll get as many different answers as there are people. Some will say "blonde" or "Wiccan", but still others will say "sweet" or "kind" or "sensuous". Her name encompasses all of her.
Now, on the other hand, these generics can be used to great affect. They can be used to show a distance between the two. This is especially affective when they first meet and are still visually new to one another. I am working on a particularly tricky scene at the moment that is too long to post, but I am using these generics to my advantage. Tara is being questioned by Willow who is a DEA agent. Tara is a radio DJ that Willow often listens to, so she has a level of familiarity with her (however distant) and constantly thinks of Tara by her name. I never utilize "blonde" or "DJ" or anything like that. She is always just "Tara". Tara, on the other hand, does not know nor has she ever seen or heard of Willow until a few minutes ago. Therefore, Willow is constantly described from Tara's POV as "the redhead", "the officer" or "the agent" until the very end when Willow promises to protect her. At the end, I tear down that barrier and she becomes "Willow".
But won't it get redundant using their names over and over? Isn't it redundant calling Tara a blonde throughout a story when we already know she's a blonde? Yes, some sentences may need a rewrite to keep from being redundant. But I have found those problems are easily solved and I usually end up with a better line anyway.
These words are walls around our characters. Our reader doesn't want to stand outside and look in. They want to roll around inside our characters hearts and heads and feel what they're feeling.
So let's tear away these walls and let them in.

I already know what they look like, even in AU where, as you so rightly pointed out, most of us see them as looking like AH or AB.
I will even agree that it doesn't hurt narrative flow, but only to a point. I can recall an example from a story I was reading a few months ago. It was AU, compelling, thought provoking. I was enjoying it. Then came an update with a smut scene. WHOOHOO!
But then at one point, the writer described Willow pulling off a particularly
smooth move but used a generic. It wasn't even "the redhead" which I could have overlooked, especially with good smut.
No, they used her job title.
Talk about jarring! I couldn't even bring myself to finish the update. There's just nothing like being tossed back in your seat and held at arms length by the writer.

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