Can tags be added to users?
AI-generated summary
A discussion on Assigning User Tags is underway. csmu inquires about adding tags to users, but pfaffman responds that only groups can be tagged. csmu explains that they are trying to help a charity determine the skills and interests of their volunteers, and initially considered using tags due to a limit on CustomUserField.
Alternative solutions are proposed, including custom badges by omarfilip, but csmu questions whether users can set their own custom badges. omarfilip suggests using groups to assign automatic badges instead. pfaffman agrees that groups seem like a workable solution, and tomtjes shares a related discussion on tagging users with interests, passions, and skills.
No. Only groups.
What problem are you trying to solve?
We’re helping a charity. They asked for a way to determine the skills and interests of the volunteers. I started using CustomUserField but ran into a hard coded limit. I thought of using tags.
I think groups will cut it.
Thanks Jay 
What about custom badges? You can easily list volunteers with specific ones. Example:
https://meta.discourse.org/badges/3/regular
Can a user set their own custom badges?
I don’t think so, but they can freely join and leave groups to which you can assign automatic badges:
https://meta.discourse.org/t/badge-sql-can-no-longer-be-edited-by-default/47894/30?u=omarfilip
Ah. That helps make sense of your questions! I couldn’t figure why you needed so many custom fields. You could get a plugin to create tags on a custom field, but groups seem like a workable solution.
See also: