My theory on Matt wearing the black suit & “DD” logo is to differentiate himself from civilian resistance supporters who may be wearing copycat Daredevil costumes/masks & become mistaken for the real Daredevil

On the one hand, it would be a good parallel to the police co-opting the Punisher logo storyline, but on the other hand it's too much like the police co-opting the Punisher logo storyline.

So this is just a fun theory/scenario I came up with. I was also slightly inspired by the Dark Knight as well. I kind of imagine the idea of DD copycats to contrast with the AVTF exploiting Frank’s skull, and in some ways be a parallel to it; using it as a story telling device for Matt coming to terms with becoming a prominent symbol of hope for the city in his fight against Fisk’s forces.

Even though people are dressing up with good intentions and want to join the fight, in a paranoid and trigger happy world, people will inevitably get themselves killed or perhaps go too far. The black suit works as stealth but would also stand out (along with the symbol) among potential copycats and allow him to become the main target against his enemies.

That’s actually my theory on why he has the double D’s. The black suit is for hiding.

Painted black for stealth and the double D's for trademark.