I  tested this and it seemed to work fine. I did have some problems with the layout (it seemed to get cutoff on the right) but that could be attributed to my custom theme. Didnt try to troubleshoot it.

http://community.elgg.org/pg/plugins/project/458332/developer/jonmaul/group-river

Thank you very much my friend. I really like this plugin and it is definitely useful. i will use it. Recommended. But, this plugin actually reflects activity of the group and some commentable things. What i wanted exactly is to make mostly everything commentable by using river_comments plugin. What i mean with that, message board, polls etc. What i dont understand with river_comment and likes plugin is that this plugin makes everything likable but not commentable. Why?

Glad it worked for you in some capacity even though it didnt really solve your issue. 

I am using an older version http://community.elgg.org/pg/plugins/project/515633/developer/pedroprez/river-comments

and the message board works. I do remeber seeing some duplicate comments...not sure about the polls

I remember at one time that I wasnt able to pick and choose and had to just pick yes for autodetect. You probably already tried this but it seemed to be worth mentioning.

I am thinking that there is a problem creating seperate comments on entries from message boards and polls. I wonder if you hit "like" on one message board entry it will show up on all the other messages that show up on the river. Have to test that one. More question than answer...anyone else have a more database centric answer?