[Plugin: WP Customer Reviews] Review button shows twice with simple facebook connect

Are you saying that simply by activating Simple Facebook Connect that it is causing the review button to show twice? If so, it’s a problem with that plugin. Our plugin uses the internal WP functions to output where it should go and has been tested with many other plugins without any issue.

bompus: No, the problem is with your plugin. It’s incorrectly assuming that the_content filter will only be run once per page in some fashion. I’d have to trace through to find the specific place where the code is being duplicated, but the_content can be run more than once.

In particular, SFC has to run the_content filter in the header to produce the content as will be displayed on the page, so it can produce proper metadata for Facebook. This content isn’t output by SFC, it’s just used internally and then discarded. So whatever you’re doing that modifies the content during the use of that filter is somehow happening in a way that causes the duplication. The modified content should be returned by the filter, nothing else should happen in, for example, the $post global.