IMO Animals are like toddlers, in that they aren't sapient enough to internalize various social rules, and stifle intrusive thoughts and instincts. I don't think dogs are wagging their tails as an uncontrollable reflex of happiness. They are happy and choose wag to their tails. If they were smarter (and did social interactions like humans), they'd be able to hold their tails.

Frowns are natural reactions when you're upset and we've learned to hide those. You can hold back a smile if you shouldn't be laughing at someone. If an adult had expressive ears and tails, I'd expect them to be able to suppress their initial reactions.

That's not to say there's no one who might have difficulties, but I wouldn't expect it to be an additional challenge.