I understand your confusion about why a post might be deleted if you have participated heavily in other forums. Many groups can become pretty toxic. I really don't mean to sound rude but like others have pointed out already, many of us are going through life altering times here and the point is that this is a SUPPORT community.
The managers of this site are not like those at the Yahoo groups to which you refer. They truly care about this community and in fact founded it upon the memory of a very dear loved one. Posts which contain disagreements have never been deleted to my knowlege.
I do believe, however, that the moderators of this forum wish to keep things from escalating out of a support community into one of those "other" sites you mentioned. I guess if we are looking for one of those "other" sites, we know where to find them.
I have seen many many respectful disagreements and have never seen anyone quarrel with those. I am thankful to be able to come here without risk of flaming and abuse at this stage of my life.