Recognizing Special Needs in Written Format

I've been thinking about a conversation I witnessed in an written online space not long ago. One of the writers struck me as special needs, though I couldn't put my finger on why. A few of the other writers seemed intent on proving that this person was "a liar" despite the supposed lie posing no risk to anyone. There wasn't much I could do to help, but it got me thinking.

How does one recogize special needs in a written format, and what can we do to be more accomodating?

Most of my experience with adapting to special needs comes from witnessing obvious discomfort or tics and trying to slow my speech and lower my volume to be less threatening until I can identify my problem behavior and adjust it. Is there a written equivalent?

Almost all of Great Grandpa Haskell’s descendants are on the Autism Spectrum. However if you see me on the streets, I rub off on others as a Neural-typical. 
You wouldn’t expect me to be told as an infant that I’d be institutionalized by 14 for my Autism/Hyperlexia diagnosis or what it took to overcome the adversity in the 90’s. My Girlfriend has ADHD and Epilepsy and we are thinking of having a surrogate youngling together. 
Special Needs, Disability and All Abilities all have diverse challenges and so you really need to get to know the person in order to really determine their needs. 
Perhaps this person in question was having an off day, the person was having an All-abilities episode or both.