I think the discussion about how to handle reputation (points connected to an account) is not finished yet? I’m a fan of giving points, but not reputation, to questions - while giving points & reputation for answers. If we go with something like that, I propose the following:
On the account page
Show a score per tag.
I don’t consider this part that important, but showing “this person knows about X, Y, and a little bit about Z” is better than “this person knows about stuff”.
For an answer
Show a score calculated from the reputation for the question’s tags.
This way, we display a value for knowledge about the question subject, instead of just general knowledge. Calculation algorithm to be done.
Using a simple average as calculation for demonstration
Question: Tags “C#” and “Database”
User A: 500 rep C#, 500 rep Database
= 1000 rep total vs. 500 related rep average
User B: 200 rep C#, 100 rep Database, 1000 rep version control
= 1300 rep total vs. 150 related rep average
User C: 3000 rep Ruby, 1000 rep jquery
= 4000 rep total vs. 0 rep related average