IMO there's a system-design question on the difference between:
1. Verified to be X (e.g. degree in biology or over 25)
2. Claims in their user-profile to be X
In practice, #1 would be expensive and hard to enforce, while #2 will get you most of the way even though it's on the honor system. Especially if it isn't used as a hard-limit on participation but instead as a convenience to others, and if you can see history to identify people who inconsistently change their own profile.
That said, for some discussions what you want it something people are unlikely to have needed to codify before, like "actually owns the same MacGuffin 4000 that I do."
1. Verified to be X (e.g. degree in biology or over 25)
2. Claims in their user-profile to be X
In practice, #1 would be expensive and hard to enforce, while #2 will get you most of the way even though it's on the honor system. Especially if it isn't used as a hard-limit on participation but instead as a convenience to others, and if you can see history to identify people who inconsistently change their own profile.
That said, for some discussions what you want it something people are unlikely to have needed to codify before, like "actually owns the same MacGuffin 4000 that I do."