Actually, if TPTB intended the scene to be humorous, they screwed up in all departments. Like, very badly. HL delivered it seriously, the music playing in the background is serious and hits the climax right after he says "I love you," and the entire episode just reeks of parallels to "Three Stories."

I do think they chose ambiguous timing. But all other things point to "he meant it." (Reminds me of his apology to Wilson in "Words and Deeds." Same kind of things.)