How-to:
- copy a link with an anchor Flow#Release_and_features_FAQ on mw.org
- create a message on a Flow board, using visual mode
- create a link on the text and paste the anchored link
- validate the link: the control fly-out displays the link with the anchor, everything looks correct
- post the message: the anchor is missing, only remains the link to the page ([[Flow]]).
No problem on wikitext mode, or if you edit the link on wikitext mode and go back to the visual mode before saving.