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Underinflation will cause damage to the tyre as well as to the wheel if you go over a pothole.

whereas overinflation will damage the sidewall if you go over a pothole/stone or even a speedbreaker at higher than normal speeds. If you overinflate the tyre you are basically leaving no room for flex since youve stretched it to the max. any impact thereafter will result in the sidewall taking the shock and since it cannot flex anymore it may get damaged.

Basically you are already putting mechanical stress on it by overinflating. hitting a pothole will have more stress on the sidewall possibly beyond it's limits.

Take a ballon for example you blow it up beyond a certain point and you are on the limit and even something so small as a poke of a finger may burst it.

For the suspension part I dont have any references it's only from experience that I'm saying that. Think about it the ride becomes hard. What that means is that the tyres are not absorbing the small bumps and are transferring it to the suspension.