Phrase Substitutions are stored in a custom theme file and this theme must be applied in order for the Phrase Substitution to take affect. If you would like to apply the substitution to specific places, you can create the phrase subs in a special theme, and then utilize the theme mapping features to only apply it to specific Groups/Spaces. Here is the documentation explaining how to apply a theme to a specific Group/Space by utilizing Theme Mapping: Jive 6.0 Community Administrator Documentation. Here is the documentation explaining how to set up Phrase Substitutions Advanced Phrase Substitution in the UI. Please remember that you need to create a special theme file first in the Admin Console > System > Settings > Themes and then make sure you select that when writing the Phrase Substitutions.