Agent Skills: Comment Cleanup

Comment Cleanup

A delete-biased pass over the comments a change added or edited. Comment quality is a whole-file property that only resolves after the code settles, so this runs on the final diff — not mid-implementation.

Scope

Review every comment on an added or edited line in the diff:

git diff --cached -U0    # or the working diff if not yet staged

Judge each comment against the tests below. Do not touch comments outside the diff in this pass.

Delete unless it earns its place

Delete a comment unless it answers one of:

• Invariant — what rule must future edits preserve?
• External contract — what protocol, wire format, consensus rule, FFI, or DB contract is being honored?
• Surprise — why is the obvious simpler code wrong (a reader would "simplify" it into a bug)?
• Safety — what makes this unsafe / panic / unwrap / lock-ordering / retry / cancellation valid?
• Workaround — what temporary exception exists, and when can it be removed?

Auto-remove (noise)

• Restating the code, the identifier, or the next line.
• A doc-comment that only expands the function name into a sentence.
• Rationale duplicated across a doc-comment and an adjacent inline comment — keep one home (the one closest to the invariant, not the more ceremonious).
• The same rationale repeated across sibling items — move the shared context to the module header or a helper comment, then keep each item's comment local.
• Names of current call sites / consumers (used by X, cross-checked in Y), tasks, PRs, or issues (handles #123) — they go stale on rename; rewrite as the invariant the code maintains. Enduring context belongs in the PR description or a design note.
• Archaeology: previously, now, added in PR, renamed from.
• Vague intent: for readability, handle edge cases, important check.
• Commented-out code.
• Loud emphasis (ONLY, SAME, WRONG, FIRST, AFTER, ACCEPTS, DIFFERS); state the invariant affirmatively without weakening it — the rewrite keeps exclusivity and requirement force ("only finalized checkpoints may be signed", not "finalized checkpoints are signed").

Every deletion or rewrite preserves scope, conditions, uncertainty, verification status, and requirement force; if the shorter form claims more than the original, keep the original.

Never remove (protected keep zones)

Leave these untouched even if terse. Protected means never silently deleted, not never edited: a protected comment whose precondition no longer holds is repaired or escalated, not kept verbatim.

• // SAFETY: on every unsafe.
• Security / consensus / crypto / domain-separation / endianness / units.
• Serialization / wire-format rationale.
• Concurrency: lock ordering, cancellation, idempotency, retry, txn boundaries.
• Migration / backward-compatibility rationale.
• Panic / unwrap preconditions.
• Public-item rustdoc stating caller-visible contract, errors, or panics.
• Test comments encoding non-obvious scenario intent.
• Generated-code markers and lint/tool directives (#[allow(...)] with a reason).
• TODO / FIXME tied to an issue or a removal condition. An untethered one is reviewed (add a condition or delete), never blindly kept.

Rewriting a kept comment

• Proportional to the code. One clear sentence over a multi-paragraph rationale. If it genuinely needs a paragraph, move it to a doc-comment on the item or a design doc.
• Affirmative, not contrastive. Describe the rule the code enforces rather than the alternative it didn't take ("checked, not saturating"; "selected by slots, not branch length"). Prefer "the target slot must precede the finalized slot; panic otherwise."
• This is not a ban on "not". Stating what invalid input does ("other branch lengths panic") is affirmative enforcement, and adversarial rationale in security code ("a prover-supplied X would let an attacker Y") explains the invariant. Both stay.
• Names must be current. Check the code before naming a helper; never carry a stale function name or an old architecture reference into a rewrite.
• Match the file's punctuation convention. If the file uses em-dashes and curly quotes, use them; if it is ASCII-only, stay ASCII.

Test comments

• Avoid "wrong reason" boilerplate. Prefer concise intent: "Positive control: the unmutated witness is accepted."
• Keep category labels consistent with the module header. If a new label such as parser-negative or positive-control appears, the header must account for it.

Finish

1. Apply the deletions/rewrites.
2. Re-run the pre-commit gate with the pass marker set, then commit: COMMENT_CLEANUP_DONE=1 ~/.claude/scripts/comment-diff-gate.sh
3. If you deliberately kept a comment that looks like noise, say so in the commit/PR rather than annotating the code.

Escalate

For diffs touching unsafe, public API docs, or crypto/consensus/security/ serialization code — where deleting the wrong comment loses load-bearing rationale — get a second-agent review of the kept/cut set rather than deciding solo.