By default?
Can't this extension become a gadget, and possibly not enabled by default? As much as the concept is a nice idea (through the promotion of friendliness), I don't see why this should be forced on all users. In my opinion, it would also be easier if it could be disabled from the gadgets' section in preferences (which is where I assume most people would look; very easily missed at the bottom of 'editing').
Actually, it started as a user script and then became a MW extension and, according to Extension:WikiLove#Installation, it can (technically) be disabled by default, but it would require community consensus for that (and likely WMF approval for that too, since this is an experiment which is being used to collect data which may help "to understand whether its usage actually affects new editor activity").
