meulog marks two things on the daily charts by itself: the deploy that went up and the watched URL that went down. Everything else that explains a strange week — the campaign that started, the trade show, the database migration, the holiday — it has no way of knowing.
An annotation is one line: the day and a short sentence. From then on, the mark shows up on every daily chart of the period, next to the deploys, so that whoever opens the screen three months later still knows why that week looked different.
Several annotations on the same day become a single mark with the texts joined: three lines glued together cannot be read. The colour is the prose ink, not a severity colour — an annotation is context, not an alarm.
Annotations are created and deleted, never edited. The value of one is being the record of what was known that day; rewriting it turns the chart into an opinion about the past.