add_comment
Post a comment underneath a wiki page (appears in the page Comments section). Use this when:
- the user says "leave a comment on page X" / "оставь комментарий"
- you want to record a note/observation without editing the page body itself
- a discussion thread needs a reply.
Do NOT use this for substantive content — that belongs in the page body via create_page. Returns: {ok: true}.