Quote Originally Posted by Trionix View Post
Why does everyone here tend to say not to describe characters in detail, such as using a full paragraph to tell the appearance details? Is it because it’s an interruption to the flow of the story? I’ve read on here that it’s an amateur thing to do, but why is that exactly?
The amount of detail should be dictated by the need for it to "characterize" a character. If the details reveal something about a character's inner strengths and weaknesses (confidence, vanity, pride, insecurity, etc.), and if those traits are important in driving the plot, then certainly include them.

Read the opening pages of George Eliot's Daniel Deronda, and note how much space she devoted to describing Gwendolen Harleth, a central character. She does it because a primary line of the story centers on Gwendolyn's character/personality. Eliot choose traits that reveal something about Gwen's personality.

One interesting technique she uses: She has other characters talk about Gwen, discussing what they like or don't like about her appearance. Here is a snippet:

In the evening the same room was more stiflingly heated, was brilliant
with gas and with the costumes of ladies who floated their trains along
it or were seated on the ottomans.

The Nereid in sea-green robes and silver ornaments, with a pale
sea-green feather fastened in silver falling backward over her green
hat and light brown hair, was Gwendolen Harleth. She was under the
wing, or rather soared by the shoulder, of the lady who had sat by her
at the roulette-table; and with them was a gentleman with a white
mustache and clipped hair: solid-browed, stiff and German. They were
walking about or standing to chat with acquaintances, and Gwendolen was
much observed by the seated groups.

"A striking girl--that Miss Harleth--unlike others."

"Yes, she has got herself up as a sort of serpent now--all green and
silver, and winds her neck about a little more than usual."

"Oh, she must always be doing something extraordinary. She is that kind
of girl, I fancy. Do you think her pretty, Mr. Vandernoodt?"

"Very. A man might risk hanging for her--I mean a fool might."

"You like a nez retroussť [turned-up nose], then, and long narrow eyes?"

"When they go with such an ensemble."

"The ensemble du serpent?"

"If you will. Woman was tempted by a serpent; why not man?"

"She is certainly very graceful; but she wants a tinge of color in her
cheeks. It is a sort of Lamia beauty she has."

"On the contrary, I think her complexion one of her chief charms. It is
a warm paleness; it looks thoroughly healthy. And that delicate nose
with its gradual little upward curve is distracting. And then her
mouth--there never was a prettier mouth, the lips curled backward so
finely, eh, Mackworth?"

"Think so? I cannot endure that sort of mouth. It looks so
self-complacent, as if it knew its own beauty--the curves are too
immovable. I like a mouth that trembles more."