I'm personally in over a 100 or more travel groups between Facebook and Reddit. Each one offers different things for different reasons in different cities and countries. As I search for new places to visit or move to I typically join at least one local and one expat based group for that city, if not several groups. It's the easiest way for me to get not only the vibe of the city/country but also information from a lived in/I live here point of view.
If you are a first time exiter of your home country, whose family and friends aren't on board with your exit, that group space is essential for your pre-move. To not only keep you motivated but to ensure that you are getting the bad, ugly and indifferent about moving and about the city/country that you are moving to. What I hope you get and what I know you will need is the "positive" energy from those who have not only done it but more importantly from those that want to do it!
Groups give you a glimpse of life in that city from a view point that may or may not match yours, they also give you the continual push you will need that those around you will not give. That doesn't mean that what you are doing is wrong! Obviously the hundreds to thousands of people in the groups would disagree.
Unfortunately I have to say, all groups aren't created equal and most don't offer as safe a space as they truly could. But don't throw the baby out with the bath water just yet, because you will need the groups, no matter what. You will also need to learn how to filter and keep the best ones popping up with the best information. With all that being said below are 5 things you should look for a in a group that may provide safe space.
1. Moderators who are active
If the moderators aren't active, exit. Trolls and folks that are not happy in that country will attack and post negative one-sided information. Moderators keep this type of activity down. I also think that groups who have more than one moderator are sometimes better in that the moderator doesn't get burnt out corralling all the personalities present in a group.
A good group will not allow just anyone to enter, the more questions/requirements the better because it also indicates the group has active moderators. Also rules help set the tone of the groups behavior.
3. Member Count
This one can go both ways. A bigger group is going to offer you more information and opinions but it also gives the trolls room to well troll. Small groups on the other hand can be to insular and cliquish.
4. Topics & Files
If the group moderators take the time to create group files or central points of interest that have been shared in the group, this is a great indicator of a group that is active and the information is good.
5. Comment Moderation
If the moderators are active then comment moderation should occur along with the closing of threads/posts that either aren't good or have reached a good conclusion. Also look for moderators who defend (to a certain extent) the city/country you are researching.