In addition to the guidelines already provided above, based on experience of moderating thousands of suggestions for the LOTRmod for Minecraft, I wish to suggest the following :
Urge people to:
only post concrete and specific suggestions. Concrete as in addressing the what, why and how. Not just "Add edible nuts to drop from some trees", but provide information on which trees, under which circumstances and give an indication on how many, how nutritious they could be and if they could be processed or have other further uses. And specific, as in no wish lists on collected random, unrelated topics.
stay on-topic in suggestion threads and in their original posts. Good on-topic feedback and discussion may lead to deviations and derivations that can initiate other new useful suggestions, so don't be too strict in it. Avoid derailing though, as that is counterproductive to anyone with an interest.
not hesitate to update original posts with any valuable insight gathered, whether that be from feedback obtained in the thread or elsewhere.
focus on suggestions to improve current features and/or well fleshed out suggestions regarding (explicitety stated) planned features.
Create and maintain a What-not-to-Suggest (WntS) list, which may include:
anything mentioned in FAQ or planned features posted by or on behalf of the developers.
any subject specifically listed in the WntS list.
anything that first requires planned features to be implemented.
easter eggs of any kind. They're the developers joy.
any imaginable real life addition unless of specific potential added value to the existing, and planned features. Vintage Story is a game with limited scope, a creation of its makers who can draw near limitless inspiration from the world. They don't need players to cough up the obvious and spam either this forum or the Discord #suggestions channel. The more noise, the smaller the chances developers will notice any useful gems hidden in the suggestion flood.
anything too obvious.
Possibly consider active moderation and/or record keeping of categorised subjects where the records are available to anyone and to be referenced by anyone considering to add a new suggestion to the bulk. Yes, that would require dedication.