Pin runEdge's moves give-up with a hand-worked line, and drop item 176

src/markdown/emit/unspellable-runs.test.ts

@@ -75,6 +75,12 @@ const lines: { carry?: string[]; drop?: string[]; name: string; nodes: AdfNode[]
     name: 'a word, strong over nodes 1 and 2, em on node 2, a word after',
     nodes: [plain('b'), marked(['strong'], '(a'), marked(['strong', 'em'], ')'), plain('c')],
   },
+  {
+    carry: ['em@2-2'],
+    drop: ['em@2-2'],
+    name: 'a digit, strong and strike over nodes 1 and 2, em on node 2, strong on a digit',
+    nodes: [plain('0'), marked(['strong', 'strike'], '_'), marked(['strong', 'em', 'strike'], '_'), marked(['strong'], '0')],
+  },
 ]
 
 for (const { carry, drop, name, nodes } of lines) {

src/markdown/emit/unspellable-runs.ts

@@ -166,6 +166,7 @@ function mayFlank(sweep: PairSweep, judged: number, character: string, end: 'clo
 function runEdge(sweep: PairSweep, judged: number, from: number, step: -1 | 1, character: string): string[] | undefined {
   const found: string[] = []
   const { delimiters } = touching(sweep, from, step)
+  // Each pair beside adds the characters it may be written with; one that stands ends the run unless it may be written with `character`.
   for (const at of delimiters) {
     const other = sweep.pairAt[at] ?? -1
     const standing = pairStanding(sweep, judged, other)