I know with the latest versions, your plugin is checking for a local "readme.txt" file and comparing it to the repository, or something very similar.
However, I've found issues with its ability to find the "readme.txt" file and how it parses the information when it does find it.
I have duplicated the issues on multiple sites, including a clean installation of WordPress.
Issue #1 - finding the "readme.txt" file: For some reason, with the "Simple Notices" plugin (http://wordpress.org/extend/plugins/simple-notices/) BPCC reports "No compatibility data found" yet the readme.txt file is very obviously included with the installation of the plugin and the compatibility data is included correctly.
Issue #2 - parsing information: The "TM Replace Howdy" plugin (http://wordpress.org/extend/plugins/tm-replace-howdy/) has a full page of information showing up in the "Description" section, at the point your plugin shows version/compatibility.
These are two specific issues, which I've found with multiple plugins, but have duplicated with the two I listed.
In both cases, the "readme.txt" file includes non-standard information (http://wordpress.org/extend/plugins/about/readme.txt) in the Plugin Name section or the readme.txt file.
In the case of Issue #1, removing the non-standard information DID NOT allow the BPCC plugin to detect the readme.txt file. I'm not yet sure of a good fix for this issue. I don't understand why the BPCC plugin doesn't see the readme.txt file.
In the case of Issue #2, removing the non-standard information DID remove the excessively long page of information from the details area. The fix is probably as simple as limiting what the BPCC plugin looks for in the readme.txt file.