Answer product-owner round 1: the changelog line says what a long run cost before, and item 33 states its cost at this commit

CHANGELOG.md

@@ -3,7 +3,8 @@
 ## Unreleased
 
 - `adfToLosslessMarkdown` and `adfToPortableMarkdown` write text holding a long run of `*`, `_`, `~`
-  or backticks, or a heading ending in a long run of `#`, in time linear in the run.
+  or backticks, or a heading ending in a long run of `#`, in time linear in the run, where a run of
+  20000 `*` took seconds.
 - **Breaking:** a list whose bullet character or ordered delimiter changes reads as two lists, as
   CommonMark reads it: `- a` then `* b`, `1. a` then `1) b`. `adfToLosslessMarkdown` gives a list
   right after one of its kind the other marker, `* ` or `1)`, in place of the `::listBreak`

todo.md

@@ -145,7 +145,7 @@ them 68188. Read most over the last five, opens and searches: `README.md` 32, `d
 
 ### 33. Emit a line in time linear in its mark runs, in `adfToLosslessMarkdown` and `adfToPortableMarkdown`.
 
-`adfToLosslessMarkdown` spends 23 s on one paragraph of 2000 × `un` plus `**-r**`: each run its
+`adfToLosslessMarkdown` spends 28 s on one paragraph of 2000 × `un` plus `**-r**`: each run its
 flanking cannot spell re-emits the whole line before riding the carry, quadratic in the runs, and
 the portable reduction's `spellableLine` drops one mark per re-emit the same way. An inline node
 whose attributes no spelling writes re-emits the line the same way before riding the carry. Make all