Try to insert a link in a visual mode of Flow:

1. Invoke popup with [[
2. Find some page and press "Insert a link"
3. The link gets inserted (the link text is underlined and blue)
4. Press space and continue typing after the link normally
5. Save the comment

What happens after steps 4 and 5:

4a. The text typed after the link is also underlined and blue and seems to be the extension of the link text
5a. However, once saved - things look as expected - the link text only grows during preview

Browser:

Mozilla/5.0 (X11; FreeBSD amd64; rv:38.0) Gecko/20100101 Firefox/38.0