docs(issue): state that the writing rules bind comments too

The four-rules header read "on create and on edit", naming only the
issue-body operations, even though the skill's scope (description,
when-to-use table, tea mechanics) covers commenting and rule 4 is
written around the comment-anchor reader. Make the binding explicit and
carve out rule 3 (a comment has no title).

issue/SKILL.md

@@ -43,7 +43,10 @@ reference issue). This skill is the shared convention they lean on.
 
 ## The four writing rules
 
-These apply to every issue, on create and on edit.
+These apply to every issue, on create and on edit — and equally to
+every comment: a comment is tracker text like any other, and rule 4 in
+particular is written around a reader who lands on a bare comment anchor.
+The one carve-out is rule 3 — a comment has no title.
 
 1. **Impersonal and tool-neutral.** Declarative voice — no "you", no
    imperative aimed at the reader, and equally no first-person narration of
@@ -98,7 +101,8 @@ These apply to every issue, on create and on edit.
 3. **Imperative, concise title.** Verb-first, one line, no trailing
    period — scannable in the list, mirroring commit-message style.
    Checkboxes (`- [ ]`) are allowed in the body for sub-points or a
-   small acceptance checklist.
+   small acceptance checklist. A comment carries no title, so this rule
+   alone has no comment analogue — the other three bind it unchanged.
    - Avoid: "parser bug" / "There is a problem with the parser."
    - Use: "Preserve backslash escapes in quoted strings"