Of course.

/u/fastfinge/ brings up some relevant points about moderation, but if the content is text-based and the software accessible, it would be just as accessible as it is to hearing blind people. (And a sighted mod might be in place for images, or a hearing mod for videos or audio content if allowed, etc)

Plus, "deafblind" just means some combined level of substantial vision and hearing loss. Some deafblind people have enough hearing to listen to a screen reader or listen to audio, or enough vision to read with high contrast or magnification, etc.

Why do you ask?

Probably. If you want, create a new subreddit and see how it goes. If I were you, I might either get a few people to help you moderate it, or automatically block all links to soundcloud, youtube, and mp3 files, as well as all image uploads and links. We at /r/blind block images, because I don't know what the image shows, so I can't tell if it's spam or not. Similarly, you won't be able to tell what the audio from a youtube or soundcloud link says, so unless you have another moderator to make sure it's not against the rules, you should probably just block it by default.

If the person is using a braille display, they could definitely run it adequately. Some collaboration might be necessary to filter out spam that might have audio, though, or spammy images, depending on what the forum allows.