After switching over my feed, I can see it had a negative effect on the Medium versions of these posts. An example. And a screen shot. 

The problem is this: my IFTTT recipe is taking the <content:encoded> sub-element of the <item> instead of the <description>.

And it seems there is no way to tell IFTTT not to do this. 

I imagine there will be similar problems in other RSS consumers.

We'll see, I guess!