You may promote anyone you like. And it's better to promote those who need support. For example in the contest, you have to find only those who didn't participate in the contest. Promoting their entries doesn't count.
But if you are promoting someone without entering the contest, you can promote even those who post in #dcc.
The goal is to spread this initiative to more new people. So, the most promoted ones will be rewarded.
How do I know they did not participate in the contest?
They didn't use #dcc tag. Only the tag of the topic. #hope in this week contest.