In UnifiedLogging, there is no OR operator (the comma is actually an XOR). This means that when you have something like -Xlog:os,gc=trace and log_trace(os,gc)("hi"), this won't print.

This turns into a bigger problem when the user wants to get messages tagged with os, gc or both. In that case, they will need to specify -Xlog:os=trace,gc=trace,os+gc=trace. With longer tag names, or in the case where we have three tags instead of only two, this results in a loss of ergonomics