Steps to replicate the issue (include links if applicable):

• Download an ePUB (for example: go to https://it.wikisource.org/wiki/Vae_Victis, click "Scarica" and choose EPUB
• Open the ePUB with your favourite ZIP software, go to OPS/ folder and open an .xhtml file (other than the front page).

What happens?:

• The generated .xhtml file contains some empty <span/> tags inside the text.
• Some ePUB reader ignore these tags and display the text just fine. In others readers like Kobo and Cervantes BQ, it is displayed an extra space which interferes with the regular flowing of the text.

What should have happened instead?:

• The <span/> tag should not be generated.

Other information (browser name/version, screenshots, etc.):

• The <span> seems to be generated by MediaWiki:Proofreadpage_pagenum_template