It is fine to discuss actions in general on the Base, but as regards any specifics (places, times, names, phone numbers), it is important to minimise your footprint as much as possible, and use E2EE (end-to-end encryption) where possible. Signal and Wire are used extensively in the French Branch, many branches in fact, for this purpose, often with message expiry and on disk encrypted phones. While it can seem an inconvenience to work across multiple platforms, it can truly save the day later, as it makes it that much harder to ever acquire a single body of evidence, a single source of concrete plans (even ascribable to intent), and so you achieve the grail of Plausible Deniability if it ever comes to the point of arrest. As always, it’s about avoiding the SPOF, the Single Point of Failure.
In short, use the Base for fleshing out ideas, working through problems, reaching agreements. But never post concretely incriminating details, especially those that can be ascribed to places and individuals. Not only is this the very fodder of the pre-arrest (the same that XR UK struggled so much with in October), but it retro-actively describes intent, and is the most of all incriminating in court.
Worth mentioning that server seizures are extremely rare, and yours is hosted well outside your jurisdiction and employs the strongest possible disk encryption.