Typically, no, as a former restaurant server I hated when customers did this because it' djust get everything disgusting and messy taking it away. 90% of the time it was worse for me. I also had a system for taking plates away, and plates that were stacked by the diner would be riskier for me then plates that I know I stacked myself. Most times when a server drops a plate and it smashed, you can best bet it's because someone stacked a plate poorly and it slid off.
Sometimes, yes, but it's typically just to indicate to an inattentive server that "I'm done with this... you should take it away..." Doesn't happen often, but at the big chains a lot of servers are clueless about letting dirty plates pile up. It's probably my biggest pet peeve, and sometimes I'll have to make room on my table when a server isn't being attentive to clean up.
Sometimes, yes, but it's typically just to indicate to an inattentive server that "I'm done with this... you should take it away..." Doesn't happen often, but at the big chains a lot of servers are clueless about letting dirty plates pile up. It's probably my biggest pet peeve, and sometimes I'll have to make room on my table when a server isn't being attentive to clean up.