I tried what you suggested, and the only thing that seemed to do was take the "so-n-so liked/commented on this post" part. So now it looks like they just posted the same thing again, but there is one more like or comment than last time. 

I thought maybe it was because of the if else statement afterwards so I tried commenting out that as well, and it seems that it didn't change anything. 

//$shouldExtend = $this->displayType == NEWSFEED_CMP_Feed::DISPLAY_TYPE_ACTIVITY && $lastActivity !== null;         //if ( $shouldExtend )        //{           // if ( !empty($lastActivity['data']['string']) || !empty($lastActivity['data']['line']) )           // {               // $data = $this->applyRespond($data, $lastActivity);           // }       // }                //if ( $lastActivity !== null )        //{           // $data = $this->extendAction($data, $lastActivity);            //$data = $this->extendActionData($data, $lastActivity);        //}

I think the change needs to be made before this point because at this point, the code has already decided it is going to make a new post from the last activity. The code above seems to just decide what it is going to do with it. 

I should clarify that if each post in the newsfeed had a number, and I went to like number 5, I don't want number 5 becoming number 1 after I like it. I want all posts to stay put. I basically want the newsfeed to behave like facebook in that sense.

Again, thanks for your quick reply and your insight @Rebecca!

See also this discussion:  https://developers.oxwall.com/forum/topic/8724