Ask The Tropers

If it's used in the indefinite sense, as a synonym for the impersonal "you", it should be OK. This is what is described in the Wikipedia article.

However, if it's used as a synonym for "I" (which is also a common usage, but is considered affected) it falls under the rule against first-person troping.

A simple test should be: if you can replace "one" with "I" and get the same meaning, then it's first-person troping and not allowed.

An example of the indefinite use: "From the reviews, one would expect this film to be bad." Here, "one" denotes anyone, and could be replaced by "you" or "the general movie-goer". This should be acceptable.

I've mostly seen it used by upper-class British women.

I think it looks weird when used several times in a row, so if that's the case, it might be best to try and rewrite the whole paragraph.

^^ One would certainly expect so, as using it in the first person is considered a mark of nobility (especially royalty).

It can add a bit of texture to writing, but it does look silly if one were to overuse it.

I find it useful to use "one" in the indefinite sense when there's a risk that using the more common "you" instead may be taken personally.

"One shouldn't do that" is impersonal. "You shouldn't do that" can be impersonal, but it could also be directed specifically at the person you're talking to, and it's a bit awkward to have to add something like "Of course I didn't mean you personally, but people in general".

It can be useful when speaking of a theoretical person of indeterminate or irrelevant gender, if one would rather not muck about with awkward "he or she" constructions or the singular "they."

In cases of indeterminate gender, no, I wouldn't use "one", merely because I don't think it's widely used for that purpose and have never seen it applied that way (the singular "they" is the most widely-accepted and the most grammatically easy to adjust to, since it's already used to refer to people the speaker has never met or learned the gender of). However, referring to the second person, "one" is okay in small doses, as long as it isn't repeated too much.

"One" is not a drop-in replacement for "he or she" or the singular "they", but you can re-write a statement to use an indeterminate pronoun instead of a personal one.

Instead of "When the player character picks up a first-aid kit, he or she gets an immediate HP boost", you could write "When picking up a first-aid kit, one gets an immediate HP boost".

I suppose that's what High Crate refers to? I think it works, but overuse of that device can seem a bit awkward. It's more direct and natural to use the singular "they".

Interesting points. I would add if when to and when not to use "one" as a substitute for "I".