The buildsys won't build packages with U+007E (tilde) in the release tag. U+007E (~) is a valid character part of the Base Latin unicode block It's a spacing character like U+005F (_) Local rpmbuild works with it happily There is no reason to block build on it (without any reason given BTW : build failed, no build logs available)
I think rpmbuild fails on this now, but even if not, the packaging guidelines say that it's not allowed. We're definitely not going to do anything about it in plague