Start of a comic.
Friend 1: "You have both DID and aphantasia, how does that work?"
Friend 2: "Second that. Are you all Aphant?"
Orion, OP's alter, looks like a satyr.
Orion: "We're pretty sure our brain signals used for mental imagery are still functional, we just don't get the visual input. It's kind of like a game map with no texture."
An example of a textureless map.
Orion: "All the information is received, but not fully processed for some reason. We used to visualize things vividly as a child, but at some point we couldn't anymore. No clue when or how."
Orion: "We all have varying levels of aphantasia. Anton has the best visual manifestation out of all of us but does not think in words the way we are accustomed to."
Anton: "hmph" written in morse code, representing the different train of thought.
Orion: "We can all imagine 'touch' and 'space' though. We feel each other's presence. That's how we figured out what we looked like! Sometimes I forget I don't need to make way for my horns."
(1/2) Aphantasia doesn't really affect our DID. It just takes longer to understand how our inner world ans us look like.