In the Deaf community, the words deaf and Deaf have two different meanings. The word deaf is used to mean someone who has a significant hearing loss, someone whose audiogram indicates they cannot hear. The word Deaf, in contrast, means someone who is an active member of the Deaf community and supporter of Deaf culture. Actual amount of residual hearing isn’t as important - it’s entirely possible for a person to be Deaf even though their audiogram labels them as “hard of hearing” or “slightly hearing-impaired.” Being deaf is a condition, being Deaf is an identity.

I have also seen a convention like this in reference to people of African or African-American descent. The word black just means someone who is dark-skinned (in varying shades), but the word Black seems to indicate pride in the subject’s African heritage and culture. What surprised me, though, was to see a acquaintance who calls himself Black make a reference to “White women.” I’m so used to capitals denoting cultural identification, that this kind of threw me. Most of the Caucasian people I know don’t tend to identify culturally with their skin tone - some may be proudly German or Greek or Italian or Polish - but they don’t make a point of being light-skinned. White supremacists might feel it’s appropriate to capitalize White, but it just felt odd to me.