[FrenchyJiby]

I'll note that France has a slight variant on that, where it's assumed that any identifiable marker of the ballot could reveal a voter's identity, bad in case of blackmail like "vote for X, and show it by having a stripe at at the top, or I [do bad things to family], I'll be checking the ballots").

To avoid this, no markers, but all possible votes are pieces of paper with printed text, grab N>2, go in the booth, put in one in an envelope.

This way your vote and any other vote look identical, and vote is voided in case of any identifying mark (even weirdly bent paper etc). No stamp needed, just number of votes/envelopes.

[ta1243]

Much larger problems with voter intimidation in the UK through the postal vote system.

I've been to several counts in the UK, spotting a specific ballot, even if you know which box it's in, is impossible.

You've then got to be able to enforce that enough to make a difference. You'd have to have a unique mark for every person (at least at every station) you're trying to enforce, one that can be quickly spotted by one of about 5 people you can get at the verification stage.

Even then there's no guarantee you didn't just miss it.

Sure, you can write "WANK" next to everyone you don't like, and that's great, but again the number of votes you could affect in this way would be a tiny number.