most modern messaging services aren't made with neurodivergent people in mind. there's so many little "features" that aren't able to be opted out of that can cause a lot more communication problems.
read receipts, [name] is typing..., online status, etc. opening the client or reading messages is communicated to everyone which can lead to a bunch of assumptions, especially in people with RSD or something else that may make them feel ignored.
and of course, someone like me might need extra time to process certain types of messages. i'm not always able to think of a response to a message in the time it takes me to read it. a lot of the time, i like to read messages as soon as they come in and reply to them later after i've had time to think on it. unfortunately, with modern messaging apps, it seems like i'm ignoring the person for hours and leaving them "on read."