Why do you consider it so strongly to be inappropriate? It literally does not tell me anything about the user.
DOS was built in a basement. Pretty sure suit and tie wasn't the dejour whilst they were doing it.
Linux was a hobby project. Pretty sure that slacks featured more than a blazer.
I will tell on myself here but having an anime pfp evokes something childish for me and I do judge the user based on it. I expect to be judged similarly because I use the album art for a favorite album of mine as a pfp on the same platform and would consider it equally inappropriate if I were to share a heartfelt and serious message like this one.