I personally wouldn't recommend this option for many adventures, BUT it can be useful to make something like a visual character tester!
So imagine you have an email or website and content creators are able to write content, you tell them, keep lines at 250 chars.
It would be cooler if they can just see how it would actually look right. In this case contenteditable is a good option.
If they actually need a wysywg editor not, if they need to save the data, not.
It's a thin line, but there are some good use-cases for it.