As someone who had COVID-19, I've researched this issue a lot.

The single case presented here did have worse symptoms from the reinfection, but we do not know the antibody status after the first infection.

Other possible cases, involving nurses and such, also had much worse outcomes after the reinfection, but I think there is a selection bias in these cases.

There is the case of a Hong Kong man who only knew about his proven reinfection because he got tested in an airport, otherwise he was asymptomatic.

There was one case of a patient remaining infected for a very long time, but his infection immediately cleared after convalescent plasma was administered, so antibodies seem to work as expected.