How do you refer to people in a statement?

Question

When reading articles like magazines and newspapers, we see a lot of people's names there, but how people are referred to varies. The following are some of the most common ones.

• First name alone
• First name + Last name
• Last name alone
• Title (Mr/Mrs/Ms etc.) + Last name
• Title (Mr/Mrs/Ms etc.) + First name + Last name

And below are some actual examples. (US President Donald Trump's case)

• Donald Trump is a man who prefers plain speaking to the language of diplomacy. (BBC)
• Trump says there's no question the coronavirus 'will go away'(CNBC)
• Mr Trump arrived for his first visit to the UK as president on 12 July. (BBC)
• President Trump Said He’s Considering Defunding The World Health Organization Over Coronavirus Response (Forbs)
• President Donald Trump reiterated Wednesday that the coronavirus will "go away," (CNBC)

Are there any commonly-accepted rules about how we should refer to people in a statement?

Answer 1

This has to do with politeness and the culturally accepted manners of a region.

When to use First and Last Names and Titles

Here are some snippets that cover specifically what you noticed:

Talking About Other People
Speaking about other people also depends on the situation. Generally, in informal situations, use first names when talking about other people
...
In more formal situations, use the first and last name

Public Figures
When speaking about public figures such as actors and politicians, there is sometimes a tendency to use a single name in a sign of familiarity.
...
For less prominent members of the same family or for people with more common names, you would use the full name, Ivanka Trump, Michelle Obama, Justin Bieber, or Brad Pitt.

First and Last Name
Use both the first and last name in informal and formal situations to be more specific when identifying a person

Title and Last Name
Use the title and last name in more formal situations. Use this form when showing respect or when you are trying to be polite

The article referenced here has many example sentences for each option.

Answer 2

Most news outlets follow a style guide that specifies these rules in minute detail. The BBC has theirs online and their section on names says the following:

Mr, Mrs etc should be used, except for convicted criminals - and also journalists, sports people, authors, actors, artists, musicians and entertainers in their professional capacity (eg: Throughout the interview, Paxman refused to be sidetracked. But: The burglars entered Mr Paxman's house.) Court reports, in the UK and abroad, should give defendants an honorific unless and until they are convicted.

The BBC is notably formal in this area (as is the New York Times). Many American news outlets follow the AP Stylebook, which says,

Always use a person's first and last name the first time they are mentioned in a story. Only use last names on second reference. Do not use courtesy titles such as Mr., Mrs., Miss or Ms. unless they are part of a direct quotation or are needed to differentiate between people who have the same last name.

As you can see, these rules from different style guides contradict each other! What really matters with a newspaper or magazine is that they pick a style guide and stick to it.

Answer 3

There are both different name formats, and different ways of addressing people, and these are really two different things. For example, you may well know a person's full name but still use only their surname out of formality. Similarly, a surname only can only identify an individual when there is no ambiguity. Situations may require that you use more names, not out of convention, but to avoid ambiguity.

Titles such as Mr, Mrs, Dr etc may be referred to as "titles" or "salutations". Sometimes they are also known as "honorifics".

A full name - forename and surname - is usually referred to as a personal name. In some specific contexts it may be called a birth name, legal name, or just full name.

A surname only is usually called a family name. Family names can be used to refer to individuals, or whole families (eg "The Smiths").

In your example where a news outlet refers to "Trump", I'm fairly certain they would have already referred to him in the article or item as either "President Trump" or "Donald Trump". Using his surname only is just an abbreviated way of referring back to someone you have already identified.

This dictionary guide explains the different situations in which various name formats might be used.