Hi Alexander,
To have the checkbox checked by default, you need to enable not one but two(!) 'Automatically link glossary entries' settings in Site administration > Plugins > Activity modules > Glossary.
Glossary
Set auto-linking checkbox of glossary entry to checked by default
Гэтае абмеркаваньне было заблакавана, таму вы болей ня можаце адказваць на яго.