diff --git a/syndicate/mc/preserve.md b/syndicate/mc/preserve.md
index f05d64e..8a36058 100644
--- a/syndicate/mc/preserve.md
+++ b/syndicate/mc/preserve.md
@@ -1402,4 +1402,10 @@ being able to avoid having to care whether the embedded value is well-
 formed or not; on the other hand, it means streaming-format embeddings
 aren't possible.
 
+TODO. The SOH-prefixed embedded binary idea is probably incoherent.
+Textual form is *text*, not binary, and since it's code-points, we
+cannot rely on having access to a hypothetical underlying bytestream.
+Remove it, and consider generalizing `#hexvalue{}` to include
+`#base64value{}` or similar.
+
 ## Notes