Bigword movement uses std::iswblank(c) and std::iswgraph(c) in its implementation, and seems to make the assumption that any character is either blank or graph (or a control character which it doesn't care about). But in the BMP alone there are 6801 codepoints (on my machine running macOS 10.15.6) that are neither blank nor graph or control. Some of these are reserved codepoints, but many are not. For example, Σ (U+03A3 GREEK CAPITAL LETTER SIGMA). Given this, the implementation should probably be using !std::iswblank(c) anywhere it uses std::iswgraph(c).

For that matter, newlines are whitespace but they aren't blank, which means bigword movement stops on every newline, which seems odd. So it should probably be using std::iswspace instead of std::iswblank (the former includes 8 characters the latter doesn't).