In general yeah, such rules can exist, but they are notoriously difficult to enforce. A long rambling story with a string of digressions, that lands vaguely back on topic is functionally hard to distinguish from a rambling story that wanders away from the poin, never to return. A bigger hurdle on that front is the specific structure of a lot of New England town meetings. Throughout the region the town meeting is considered a core part of governance, so the topic at hand is frequently anything within the governance of the city. It is a far more expansive view of public participation than is even seen in most of the US.
In most of these situations I’ve found that a better approach is tightly monitored time constraints and a defined section for public comment. Give the loons their time, protect their time, but enforce that they only get to interrupt during their time. Give everyone their 3, 5, 10 minutes or whatever, then enforce it. It is content neutral and tends to reduce the crosstalk and cheering that lets the fringe run the most wild.
