I’m not sure what problem that solves that crossing voters of a list doesn’t already solve. What about mail in and early voting?

It’s a fun way to add flare to voting day.

It’s only fun if you want people to know you voted. Not everyone does.

From a IS centric POV, are there communities where voting is looked down upon?

I was mostly thinking people in coercive relationships.

But in terms of communities it might be that voting is looked down upon for certain members of that community not the community as a whole.

In broader terms while marking people who have voted may not reveal who they voted for it does reveal that they did vote. This is less private than the election authorities maintaining the record of who has voted.

I suppose it could help with duplicate voting since some places don't require ID to vote.

ID requirements do practically nothing about duplicate voting.