"Fortunately, reddit’s then-CEO, Yishan Wong, allowed him to keep his job and continued paying him until he was ready to work again"
So he worked for the company from 2012-2015..3 years. It sounds like at least a year of this was spent in and out of the hospital and he continued to get paid. It's not like he was fired on the spot.
Reddit gave him plenty of recovery time..and it just didn't work out in the end. I see no problem with what they did.
"Victoria (aka /u/chooter) was, without question, one of the nicest, most passionate, most efficient workers at reddit, and I honestly can’t fathom why she would have been terminated. It was such an honor to work with her, and as many mods have already stated, she truly took her work to heart and tried to provide a service to the community. She was one of the most well-known admins and was just incredible at her job. Without her, there would be hundreds of incredible AMAs that would have never happened."
We only see one-side of the story. Why was she let go? We still don't know.