The error occurs when WordPress receives a comment identifier that does not match any record in the wp_comments table. Core functions such as wp_update_comment() validate the ID and return a WP_Error object when the lookup fails. The check also verifies that the associated post exists and that the current user holds the edit_comment capability.
Typical triggers include a deleted post, corrupted comment rows, stale object‑cache entries, or code that passes an incorrect ID. When the validation fails, WordPress stops processing and returns the “Invalid comment ID” message.