Thread:User talk:CodeCat/Template:grc-part-1&3/reply

is a script template, and all script templates have a face= parameter. There are several possible values and one of them, 'head', is used to show the term in headword-line formatting. The reason this is part of the script template is because not all scripts show headword-lines the same. Hebrew for example doesn't use bold, it makes the text bigger instead.