If he's bitter about his ex does that mean he's not over her?

If someone brings up her name he goes on a rant about all the bad things about her. This makes me feel like he's bitter because maybe there's still feelings there. Otherwise, why would he care? My ex turned out to be a jerk, and I'm not bitter. I'm not concerned with his life at all. What do you think?
If he's bitter about his ex does that mean he's not over her?
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