The ease with which I can add/remove members from my groups makes this service very appealing! It's also helpful that every member has their own space within each room so if one person disappears or leaves they don't affect others in any way (other than being annoyed by them!).
Sometimes when replying comments people are unable reply because other users aren’t there as well; would be great for more private discussions between 2 particular individuals who may wish privacy over public comment threads where anyone could read what was said without needing permission first via PM etc.. However having different spaces allows me flexibility about whom i choose invite into certain rooms at times like during work hours vs evenings time periods / holidays & weekends.