Hello! I submitted this bug to Fandom, but they said the problem was in the extension and suggested I contact the author. Here is the text of the bug I submitted. For context, the "legacy" system is running MW 1.19 and the UCP is running MW 1.33.3. Thank you for reading :)
This problem is present on both legacy and UCP.
It is my understanding that <poem compact> should suppress the generation of <p> tags, but it is wrapping the text--starting with line 2 and ending with the next-to-last line--in a <p> tag. This adds margins in the middle of the poem which should not be there.
***ON UCP, in preview, the rendering is correct. Once you save the file, the error appears.***
On legacy, the rendering is incorrect on both preview and saved changes.