I installed a bigger update today which seems to have broken the development feeds.
I asked for help on the discourse forums:
Edit: a few more site updates coming, as I need to test things without one plugin.
Things should be back to normal in 30 minutes.
Edit: so currently (until the reaction plugin gets an update) the choice is between having it (though it might still not work correctly), and having the development feeds broken. Or having everything else except the post reactions working.