Different results in Firefox 55 and Chromium 60 (linux)
- Edit https://www.mediawiki.org/w/index.php?title=User:Quiddity_(WMF)/sandbox2&oldid=2544402 in classic wikitext mode (or same at metawiki)
- Select all (either manually or ctrl-A)
- Click one of the <opening></closing> links/buttons in MediaWiki:Edittools under the save button, e.g. <translate></translate> or <code></code>
- Firefox: the entire block is replaced by, e.g. <translate>-</translate> (dash in middle)
- Chromium: nothing changes
Note: Removing any text from that example will result in it starting to work properly. It is currently 1001 bytes (possibly relevant?).
I first encountered this bug whilst trying to markup content for translation.