I have chosen this because upvoting comments is not a good option for smaller accounts. They need to either use also @dustsweeper or delegate enough to get more than a 0.02$ upvotes. Otherwise the upvote will simply be erased after 7 days. That requires about 50sp now, not terribly much, but it would exclude all minnows for being able to use me.
Also in this way you can be sure that the vote always ends up on your main posts, not upvoting some random comment you made at the wrong time.

The change in code would actually not be that big, maybe I will make a poll from my delegators to see if they would support such a change.