diff --git a/src/bytes/buffer.go b/src/bytes/buffer.go
index f90d9eca0f..9684513942 100644
--- a/src/bytes/buffer.go
+++ b/src/bytes/buffer.go
@@ -21,6 +21,12 @@ type Buffer struct {
 	buf      []byte // contents are the bytes buf[off : len(buf)]
 	off      int    // read at &buf[off], write at &buf[len(buf)]
 	lastRead readOp // last read operation, so that Unread* can work correctly.
+
+	// Copying and modifying a non-zero Buffer is prone to error,
+	// but we cannot employ the noCopy trick used by WaitGroup and Mutex,
+	// which causes vet's copylocks checker to report misuse, as vet
+	// cannot reliably distinguish the zero and non-zero cases.
+	// See #26462, #25907, #47276, #48398 for history.
 }
 
 // The readOp constants describe the last action performed on
diff --git a/src/strings/builder.go b/src/strings/builder.go
index e6df08c6f4..7ecef3176b 100644
--- a/src/strings/builder.go
+++ b/src/strings/builder.go
@@ -23,6 +23,12 @@ type Builder struct {
 	buf []byte
 }
 
+// copyCheck implements a dynamic check to prevent modification after
+// copying a non-zero Builder, which would be unsafe (see #25907, #47276).
+//
+// We cannot add a noCopy field to Builder, to cause vet's copylocks
+// check to report copying, because copylocks cannot reliably
+// discriminate the zero and nonzero cases.
 func (b *Builder) copyCheck() {
 	if b.addr == nil {
 		// This hack works around a failing of Go's escape analysis