This page hasn't been updated for Beta findings.
Mailchimp style guide recommendations
This style guide was recommended in Alpha. We discussed this topic again in Beta and will be updating this page to fully reflect that discussion. For now we have removed some guidance that didn't sync with that discussion.
All the below is from https://styleguide.mailchimp.com/writing-about-people:
"We write the same way we build apps: with a person-first perspective. Whether you’re writing for an internal or external audience, it's important to write for and about other people in a way that’s compassionate, inclusive, and respectful. Being aware of the impact of your language will help make MailChimp a better place to work and a better steward of our values in the world. In this section we'll lay out some guidelines for writing about people with compassion, and share some resources for further learning.
Age
Don’t reference a person’s age unless it’s relevant to what you’re writing. If it is relevant, include the person’s specific age, offset by commas. For example, "The CEO, 16, just got her driver’s license."
Don’t refer to people using age-related descriptors like “young,” “old,” or “elderly.”
Disability
When writing about a person with disabilities, don’t use the words “suffer,” “victim,” or “handicapped.”
Gender and sexuality
Don’t call groups of people “guys.” Don’t call women “girls.”
Avoid gendered terms in favour of neutral alternatives, like “businessperson” instead of “businessman.”
If you are referring to a known person who identifies as male or female, use ‘she’, ‘her’, ‘he’ ‘his’ etc freely. Otherwise use ‘they’, ‘their’ etc.
When writing about a person, use their communicated pronouns. When in doubt, just ask or use their name.
Hearing
Use “deaf” as an adjective to describe a person with significant hearing loss. You can also use “partially deaf” or “hard of hearing.”
Heritage and nationality
Don't use hyphens when referring to someone with dual heritage or nationality. For example, use "Asian American" instead of "Asian-American."
Conditions
Do not refer to a person’s medical, mental or cognitive condition unless it’s relevant to what you’re writing.
Vision
Use the adjective “blind” to describe a person who is unable to see. Use “low vision” to describe a person with limited vision."
Source: https://styleguide.mailchimp.com/writing-about-people/
Usability evidence from Beta
GOV.UK Inclusive language: words to use and avoid when writing about disability, 2018
https://www.gov.uk/government/publications/inclusive-communication/inclusive-language-words-to-use-and-avoid-when-writing-about-disability
Scope 'The social model of disability', 2018
https://www.scope.org.uk/about-us/our-brand/social-model-of-disability
'Disability is not a dirty word: Moving away from "special needs"', 2018
https://thespinoff.co.nz/parenting/26-03-2018/disability-is-not-a-dirty-word-moving-away-from-the-term-special-needs/
US government on inclusive language, 2017
https://content-guide.18f.gov/inclusive-language/
'A disability is a mismatch between a person’s abilities and their environment', 2016
https://medium.com/@mosaicofminds/a-disability-is-a-mismatch-between-a-persons-abilities-and-their-environment-cc39e29e8e74
'The Conscious Style Guide: How to talk about people with inclusive and tactful language', 2016
https://zapier.com/blog/communicate-inclusion-and-diversity/
Mailchimp style guide, 2015
https://styleguide.mailchimp.com/writing-about-people/
GOV.UK on inclusive communication, 2015
https://www.gov.uk/government/publications/inclusive-communication
Mailchimp is a US company. Americans tend to use the term 'people with disabilities' but UK disability charity Scope uses the term 'disabled people' because we subscribe to the social model of disability.
This model of thinking says:
• people don’t ‘have’ a disability (they have an impairment such as Cerebral Palsy or Autism)
• people are disabled by society’s barriers (such as information in an inaccessible format or lack of level access).
The social model of disability was developed by disabled people. It says that disability is caused by the way society is organised, rather than by a person’s impairment or difference. It looks at ways of removing barriers that restrict life choices for disabled people. When barriers are removed, disabled people can be independent and equal in society, with choice and control over their own lives.
[https://www.scope.org.uk/about-us/our-brand/social-model-of-disability]
I couldn't see anything about the impact on readability in the research (though clearly it has a bearing on how people feel about what you write).
But I did find a little more on inclusive style, which MailChimp appears to have drawn from.
This article summarises the Conscious Style Guide approach, https://zapier.com/blog/communicate-inclusion-and-diversity/, and the guide itself is here: https://consciousstyleguide.com/about/ (though it seems to me to be more an aggregator of links to how representative groups for particular identities prefer to have language used.
The US Government page on inclusive writing is here: https://content-guide.18f.gov/inclusive-language/ - it seems based on the Conscious Style Guide.