The canon way to express thanks would be kogaan.

There's a variety of reasons why someone might still use the Legacy dictionary. Some are longtime members who helped contribute to that dictionary and have a personal attachment to the words. Some might find it more accessible and use the Legacy dictionary to carry casual conversations with their friends. Others might like the variety it has to offer and choose to use those words because they don't want to be restricted by canon.

Even though our dictionary, lessons, and contests have moved to canon-only, we'd like to stress that using the Legacy dictionary isn't wrong or incorrect. It's there for the people who'd like to use it, and those of us who prefer canon only (myself included) can simply ignore it.

One of the reasons we switched to canon-only material was because it wasn't always immediately clear whether something was part of the official language or if it was fanmade. For anyone using Legacy words outside of the site, or even here on the site, we encourage you to label it so anyone who stumbles across it doesn't mistake it for the official language.