I try reproduce this situation on demo.moodle.org...
For ASCII characters it works without problem, for russian characters - don't work...
Added bug-report MDL-6596
Glossary
Match whole words only
ការពិភាក្សាត្រូវបានបិទ ដូច្នេះអ្នកមិនអាចឆ្លើយតបទៀតទេ។