add clarification

Author: franz1981

core/src/main/java/io/netty/loom/EventLoopScheduler.java

@@ -221,6 +221,9 @@ public boolean execute(Thread.VirtualThreadTask task) {
       }
       var currentThread = Thread.currentThread();
       if (currentThread != eventLoopThread) {
+          // currentThread == carrierThread iff
+          // - event loop start
+          // - Thread::yield within this scheduler
           if (currentThread != carrierThread) {
               // this is checking for "local" submissions
               if (currentThreadSchedulerContext().scheduler() != sharedRef) {