It can be abused if every newbie account that just registers gets a startup merit as you think. Do you believe that everyone has the skills to register more than one account?
It is not right to manage accounts alone, it is a bad thing for the forum. Nowadays, many account farmers keep many accounts in reserve on their farms. However, this is not right. If an account can be promoted well, it is best. Seeing the amount of good reach that can be achieved by putting effort into an account, it is impossible to do well if you have one.
That is why one account is best. It will be best if you can move forward well by posting good quality posts, using your creativity, and creating a good position in the forum. If you can post good quality posts, achieving merit is not too much trouble.