diff --git a/internal/jsonrpc2/jsonrpc2.go b/internal/jsonrpc2/jsonrpc2.go
index cdbc3dce7c5..f1c1a1f3c92 100644
--- a/internal/jsonrpc2/jsonrpc2.go
+++ b/internal/jsonrpc2/jsonrpc2.go
@@ -300,6 +300,8 @@ func (r *Request) Parallel() {
 // You must call this exactly once for any given request.
 // It should only be called from the handler go routine.
 // If err is set then result will be ignored.
+// If the request has not yet dropped into parallel mode
+// it will be before this function returns.
 func (r *Request) Reply(ctx context.Context, result interface{}, err error) error {
 	if r.state >= requestReplied {
 		return fmt.Errorf("reply invoked more than once")
@@ -310,6 +312,10 @@ func (r *Request) Reply(ctx context.Context, result interface{}, err error) erro
 	ctx, st := trace.StartSpan(ctx, r.Method+":reply", trace.WithSpanKind(trace.SpanKindClient))
 	defer st.End()
 
+	// reply ends the handling phase of a call, so if we are not yet
+	// parallel we should be now. The go routine is allowed to continue
+	// to do work after replying, which is why it is important to unlock
+	// the rpc system at this point.
 	r.Parallel()
 	r.state = requestReplied
 
@@ -380,6 +386,9 @@ type combined struct {
 // It must be called exactly once for each Conn.
 // It returns only when the reader is closed or there is an error in the stream.
 func (c *Conn) Run(ctx context.Context) error {
+	// we need to make the next request "lock" in an unlocked state to allow
+	// the first incoming request to proceed. All later requests are unlocked
+	// by the preceding request going to parallel mode.
 	nextRequest := make(chan struct{})
 	close(nextRequest)
 	for {