Skyspell highlighter doesn't seem to work in scratch buffers.
Steps to reproduce:
echo "mispelling" > test.txt
cat test.txt | kak -n -e 'eval %sh{skyspell-kak init}; skyspell-enable en_US'
kak -n -e 'eval %sh{skyspell-kak init}; skyspell-enable en_US' test.txt