They don't read the reports; rather, their report system applies penalties automatically when an account is reported a sufficiently high number of times.
On the one hand, it's good news because you have a 100% certainty each and every one of your reports matters; on the other hand, it's bad news as it means if enough people who don't like the fact you picked widowmaker and refused to switch report you, you'll get that automatic penalty too, see for example this thread on reddit:
http://bit.ly/2fSH9nf.