Unless they spam them unnecessarily after every single play that's made, they mean exactly what they're supposed to mean. To imply they mean otherwise by default is just cynical.
It takes one hell of a spam fest to get me to squelch them too.
I watch a lot of highlight videos on YouTube like from hearthstone SparkTV. I noticed that a lot of the pros who don't squelch often send and receive "hello" after some really bad luck or right before doing massive lethal. To me, it's almost like "you're so bad that I forgot you were even there so 'hello'".
I don't use emotes very often. If my opponent greets me at the start of a match I'll greet them back, and I'll sometimes use "wow!" if ridiculous RNG happens.