Sorry to say both of the things you mentioned don't earn Xpers. - You get points for posting opinions, but not opinion comments - You get 1 Xper point each time you are followed by someone, not vice versa.
No, you don't earn Xper points for commenting on others' opinions. You don't get Xper points for following someone either.
How to earn Xper points: - Signup +10 - Login per day +10 - Set Relationship Status +10 - Set Personality Type +10 - Set Occupation +10 - Upload Custom Avatar +50 - GirlsAskGuys Anniversary +100 - Birthday +100 - Ask a question +1 - Question gets more than 10 opinions +5 (we will check to see if duplicate accounts, which will be cancelled) - When you select Most Helpful Opinion for your question +2 - Article Comment +1 - Article gets more than 50 ups +10 (we check for duplicate accounts, which are cancelled) - Connect Facebook Account +100 - Connect Google+ Account +100 - Share GirlsAskGuys on Facebook +100 - Share GirlsAskGuys on Twitter +100 - If you are Followed by a GirlsAskGuys member +1 - Share your opinion on a question +1 - You got Most Helpful Award +5 - You shared your opinion within 15 minutes after the question's asked +1 - Your opinion is the first opinion from your gender +1 - Share your opinion on a Featured Question +1