Wikipedia:Endorsements

Apparent commercial endorsements of goods, services, businesses, companies, nonprofits, and famous persons present special editorial challenges that require particular care.

Political endorsements
An RfC on inclusion criteria for lists of political endorsements in December 2019 concluded that endorsements from an individual must meet all three of the following criteria for inclusion on a list of endorsements:
 * 1) The endorser must have an article or be unquestionably entitled to one
 * 2) This endorsement must be covered by reliable and independent sources
 * 3) Coverage of the endorsement needs to use the word endorse, or other closely related synonym.

For organizations (including the media) there is consensus for criteria 1 and criteria 3, and no consensus for criteria 2.

Using or liking vs. endorsing
Using or liking something and endorsing it may not be the same thing. One notable person who formerly was elected into government and wore one brand of wristwatch and later entered private life and made several times the annual income wore another brand of wristwatch, probably much more expensive. That should not be reported as an endorsement of either brand, unless sourcing supports reporting it as an endorsement.

Famous persons as akin to products and companies
Persons are relevant to Wikipedia as both endorsers and endorsed. Famous persons are often endorsed. They're included here because, as identities, many have become brands in their own right. A picture of a famous actor and an apparent fan when the second person actually is not a fan may violate the second person's right of publicity and be contentious.

Compensation
Paid or compensated endorsements are considered to be different from those that are free and, if they are known from sourcing to be compensated, should be reported as such. However, in most cases the endorsements are not significant enough to be reported at all in Wikipedia, unless, for example, they are controversial or a major part of a person's income.

Models
Modeling is often a form of endorsement, depending on context. For example, a woman modeling a dress for a fashion magazine's editorial pages may not be commercially endorsing the dress or the magazine but the same woman may model the same dress in the same imagery in an advertisement, thus commercially endorsing the dress or other product or service.

Long-term endorsements
Endorsements lasting for explicitly extensive time, such as when someone enters into a multi-year endorsement contract, are reportable as such, but only if a reliable source supports the statement.

Past tense or "as of" date preferred
If a person apparently has made a commercial endorsement, it should be reported only in the past tense, as occurring "as of" a stated date, or by using another formulation to similar effect, as the person may have a legal right of publicity limiting use of their likeness in advertising or for trade and the endorsement may no longer be true and use of the present tense may be contentious. Especially because many endorsements are only for short periods of time, the use of a present tense should be limited to a few weeks after the publication date of the latest reliably sourced report on point. If the publication date is uncertain or if the source is itself in the past tense, the present tense should be avoided. As an editor may not return to edit an article a few weeks later, the past tense is probably more prudent at any time.

Reliable sources
An advertisement or advertising campaign by itself should not be considered as the necessary reliable source, although it may be cited along with another source. That is mainly because the advertisement is a primary source and the person's actual opinion about the product may not be accurately represented by the ad. Consumer or industry news media about the advertising are more reliable as sourcing about the fact of the endorsement, although not about the endorser's personal opinion, for which another source may be needed.

Weight
Most endorsements are not reportable because that would be giving them undue weight. In some cases, actors or sports stars will do a huge number of endorsements, and so to list every product endorsement would be to give these endorsement deals undue weight. In these cases, it may be preferable to say "Celebrity X had a number of endorsements" with a citation. For example, one notable entertainer's hair caught on fire during the filming of a commercial, which traumatized him, probably affecting his subsequent career for years; even if the fire was accidental and the product did not fuel the fire, the commercial and the related product endorsement would likely be reportable as having due weight.