They might look tacky in first place, but I assume they are related to the dollar signs in the stacktraces of code with threading and anonymous functions. :)

    ...
    at com.company.IdentityVerifier$$anonfun$go$2$$anonfun$apply$2.apply$mcII$sp(IdentityVerifier.scala:19)
    ...
    at com.company.UserCreatorMain$1.run(UserCreatorMain.java:37)
    ...

Agreed.

I look at Scala stacktraces fairly often (but not that often, because static typing) and I didn't get the dollar signs until I read the blurb on their page. Notice that Scala doesn't replace S with $ as they're done, but rather puts $s around words. I think it would be better to use a headline like

Make Sense of your $Scala$$stack.trace