Yes, to include all the text on the main file is very helpful for translation process.
But it also helpful if WPMU provide any example PHP files for each of wdf template file (thank you, etc), not only provide fundraiser_template.txt, so that examples files will be helpful also for doing customization.
It is very important that WPMU can provide us the example PHP files of each WDF templates (single fundraiser, checkout and confirmation), not only the note fundraising_template.txt. So we can take a look into the file, then we can make any modificaiton.
Or WPMU can place the default message of thank you etc to the WYSIWYG editor on the plugin setting, so we can live edit the default message. Then provide us to the buttom for reset or back to the default message.
Very important for every user of this plugin to customize the message for serving clients better and personally.