Can "his/her" be replaced by "his"? [closed]

You can use the singular “their”: “what happens to their account”.

While is was regarded with rather less than more favorability in the past by style guides, it is gender-neutral and, as such, regains popularity.

Using "their" is probably the best alternative if you insist on avoiding "his". The downside is that it implies plural and sounds slightly awkward.

I consider using "his" in a gender-neutral context still acceptable. If somebody takes offense at common pronoun usage (with broad historic precedent), they're actively nitpicking for reasons to get offended, with no intent of having a productive discussion.

The unwieldy construction "his/her/whatever-the-pronoun-is-for-transgender" is drawing attention away from your topic to gender issues. Good to avoid unless you're specifically writing on gender.

Your example of using "the" is actually changing semantics of the sentence. It amounts to rephrasing, not just simple replacement of a pronoun.

Alex died without depositing money to Drew's account. If Alex dies, what happens to the account?

In this example, "the" denotes Drew's account. However, any pronoun (his/her/their) would denote Alex's own account.

I agree that 'they/them/their' is and has been for a good long time a grammatical and reasonable [more reasonable than 'his'] use with grammatically singular but notionally plural pronouns.

The 'his' alternative was an artificial construct that was meant to try to stop what was a natural language use. What's worse, it attempted to end the use of 'they/them/their' based on a misconception about English pronouns.

Grammar Puss ...

Sometimes an alleged grammatical "error" is logical not only in the sense of "rational," but in the sense of respecting distinctions made by the logician. Consider this alleged barbarism: Everyone returned to their seats. If anyone calls, tell them I can't come to the phone.
No one should have to sell their home to pay for medical care.

The mavens explain: [everyone] means [every one], a singular subject, which may not serve as the antecedent of a plural pronoun like [them] later in the sentence. "Everyone returned to [his] seat," they insist. "If anyone calls, tell [him] I can't come to the phone." If you were the target of these lessons, you might be getting a bit uncomfortable. [Everyone returned to his seat] makes it sound like Bruce Springsteen was discovered during intermission to be in the audience, and everyone rushed back and converged on his seat to await an autograph. If there is a good chance that a caller may be female, it is odd to ask one's roommate to tell [him] anything (even if you are not among the people who get upset about "sexist language"). Such feelings of disquiet -- a red flag to any serious linguist -- are well-founded.

The logical point that everyone but the language mavens intuitively grasps is that [everyone] and [they] are not an antecedent and a pronoun referring to the same person in the world, which would force them to agree in number. They are a "quantifier" and a "bound variable," a different logical relationship. [Everyone returned to their seats] means "For all X, X returned to X's seat." The "X" is simply a placeholder that keeps track of the roles that players play across different relationships: the X that comes back to a seat is the same X that owns the seat that X comes back to. The [their] there does not, in fact, have plural number, because it refers neither to one thing nor to many things; it does not refer at all.

On logical grounds, then, variables are not the same thing as the more familiar "referential" pronouns that trigger agreement ([he] meaning to some particular guy, [they] meaning some particular bunch of guys). Some languages are considerate and offer their speakers different words for referential pronouns and for variables. But English is stingy; a referential pronoun must be drafted into service to lend its name when a speaker needs to use a variable. There is no reason that the vernacular decision to borrow [they, their, them] for the task is any worse than the prescriptivists' recommendation of [he, him, his]. Indeed, [they] has the advantage of embracing both sexes and feeling right in a wider variety of sentences.

http://pinker.wjh.harvard.edu/articles/media/1994_01_24_thenewrepublic.html