@dcent Ok, now I got:

patching file display.css
Hunk #17 FAILED at 1224.
1 out of 17 hunks FAILED -- saving rejects to file display.css.rej

About the answer: I don't think Javascript is involved. If you hover the "in reply to" of your notice (the one starting with "BTW"), you'll see that it is, indeed, a reply to your previous notice (the one starting with "Np"). It would have notified me if it were an answer to one of my notices.

I tend to manually insert the handle of the account I'm writing to, as it would not produce notifications for mastodon (and maybe pleroma) otherwise.