I have sometimes had a look at these places, expecting to find ways of contacting members of these communities for various purposes linked with postcards. I aim a bit put off by seeing that actually very few post crossers seem to interact within/through these communities, many posts date back to months or even years… Sometimes I see moderators or other users advising someone to post in there, but my own experience is that you reach a wider audience by posting on the general English language main areas.
My question is: are there many users of these communities? How useful do you find them? Can you mention cases where they have been really useful?
I am not meaning they are useless, but that they seem to be under-used and that is a pity. Your thoughts about that?
Singapore is too small - but I would love to see an ASEAN section in the Language & Geographical Communities!
I guess it varies from the different communities. For example, I live in Norway so I am in the Scandinavian community. Unfortunately we are a very small community, so there’s not too much activity in there. We have a general thread about everything, where we write in our mother languages (Norwegian, Swedish, Danish) and one thread in English, visitor’s corner, where there is not so much activity either.
In the German community, which have a lot more people active, there is also a lot more active threads.
Even though the Scandinavian countries have active members on the main site, very few of these are active in the forum, or some of them are active in other parts of the forum.
The German language community is very active and is used for lots of different purposes, including tags, rr, other games, chatting (postal related and general), pre-planning of meetups, swaps, pen pals, help topics and many more 
It is a pity, I agree. There was an iniciative in CZ during covid to send postcards to clients in retirement homes to cheer them up. I had to make a post about it in the meetup category in order to be actually seen by people. Although I explained the reasons in the post, it was later moved out of sight to the community section. There isn’t even a Czech section, you have to go to Other Languages & Regions. I would never post there, nobody will find your thread.
I occasionally visit the Chinese community forum, but most posts are questions or discussions. The activity level has significantly dropped compared to before the significant blocking of addresses in mainland China. Due to this incident, all posts in the Chinese community now require administrator approval before publication. 
This restriction could be reconsidered. I’ve been contemplating emailing the administrator to discuss this issue soon. 
The North American language community is relatively active with a good number of Tags and Round Robins exclusive to it. Some of those Tags or Round Robins have bigger equivalents in the Forum as a whole so people can do both or choose for the cozier NA version or a more diverse Forum one.
Yes, if it is about something that specifically concerns a certain country, then we move a request to this Language & Geographical Communities .
Experience shows that even if the community is not very active, such country-specific queries will still be answered if there are active forum users from that country - as long as they are able to answer the specific question, of course.
The British Isles (name controversial) section is active with a small group of dedicated supporters. It is the place to go for questions about Royal Mail and suchlike 
The Russian language corner is rather active and pretty cosy (for most of the times)) I would not call it crowded, but there are permanent participants and lots of activities. As far as I know some of the participants prefer this section both to international and even to official swaps. I like this tiny “community in the community”.
We’re relatively active in the Oceania section — mainly Australians, of course!
In particular we have an Australian thread called ‘have a yarn’ (yarn = chat). It’s the place to find virtually any Australian forum folk.
It does make sense for the moderators to redirect some posts to a more precise community, but maybe it should be possible to have the posts appear both, possibly in different languages, in the general page and in the more limited community, which is definitely visited by less persons and therefore a bit “neglected”???
I have to apologize a bit about having been somewhat hasty in wondering about the relevance of the Language and regional Communities, this was due to my mostly having a look at a few of them, especially the French language one. Then reading the other posts, I was curious to see about more and discovered that actually some of these groups were rather active, especially the "British Isles " one, but not only. The problem with the French language community may be that there are not enough very motivated French-speakers to use it, in spite of French being spoken not only in France but in a big part of Belgium and Switzerland, as well as also in Canada and in a number of countries where many people use it beside their own language.
However, I still think that it would be great to be able to post a similar text both in the general area AND in a more limited community. For instance, if I am looking for cards from a French-speaking country and am not adamant about sent from origin, there may be persons in a non-French-speaking country who would have some cards I try to get for trade.
Thanks to everybody who has contributed to this thread, it was very interesting!
Living in the Netherlands, the Dutch language (NL and Flanders-Belgium) forum seems fairly active especially the games section.
I recently found the French RR thread (the rest seems fairly dead), which was restarted a few months ago. It seems fairly active but is complicated as indicated here above, it’s not country specific. For me ideal since I don’t live in a French speaking country but an great way for me to keep my (nearly) native French language active.
In these 2 languages it seems the RR threads are the most active.
It might also depend on who the moderator is . On the Dutch part of the forum the moderator is @JetteLise who is also active on the international RR threads…