For me, forum RP scratches a very different itch than tabletop. Players enter tabletop games content with the idea that random chance will play a big role in their journey; in forum rp, the journey is up to the players and GM to plan out and design themselves. 

To that end, character death and injury is usually planned out well in advance and serves a specific purpose in the story, rather than being unexpected like it would be in tabletop. To use someone else's example, your MMA fighter wouldn't get injured and leave you figuring out where to take his story next, but rather you would probably have suggested the injury yourself because you want to take your MMA fighter through that lifestyle change and explore how it affects him. 

If I were GMing, that's how I'd handle it, though I think you'll find this issue breaks pretty cleanly on tabletop vs non-tabletop people lines, lol.