FBI Director Comey is an honorable man and it’s unfortunate that he’s being attacked. He is a Republican former US Attorney. He understands more about mens rea and criminal intent than all the talking heads and Twitter trolls combined. Everything that people do that is wrong is not criminal, and everything that is criminal is not prosecutable (is that a word?).
Clinton was wrong to use a private server, it increased the possibility of foreign interception. That is poor judgment and a reason not to vote for her but in the opinion of the professionals who reviewed the case, not enough to prosecute.
One last thing, people who say other S of S also used two email accounts miss the point. They did so to separate work from personal. Clinton didn’t use two emails – apparently she chose not to use her government account, putting all work emails on her private server.
In doing so, she increased risk of exposure to sensitive materials and kept control of public disclosure in her hands rather than the government. The FBI found business emails that Clinton didn’t disclose, unintentionally apparently, but that is no excuse. Ironic that she increased chances foreign agents would get information they shouldn’t but decreased chances public would get information they should.