This is not the answer but a trick…
In BP you have a folder named bp-languages. In it there is a .pot file. Open it with a texteditor and search the expression. You will find file name and line #
This is avaible for ALL phrase, alerts, message or other expression found in BP.
I have tried changing the text in the .pot file as you suggested but I still get this original message:
Sign Up Complete!
You have successfully created your account! To begin using this site you will need to activate your account via the email we have just sent to your address.
QUESTION: Any suggestion on where I can change this message? I also tried to change it in wp-content/plugins/buddypress/bp-themes/bp-default/registration/register.php, line 225 BUT also that did not work to change the message.
Don’t hardcode the BP files, use child theme to make changes
The POT file is the catalogue. You have nothing to change in it.
The PO file is the work file
The MO file contains the PO compilated datas who will be read by WP
If you want to modify BP messages or different text, you have to edit a PO (without T) file. Use poEdit (or equivalent)
When you save the file, poEdit creates automaticaly a compilated mo file Your modification will be in this file, and this file had to be in the right folder on your site !
Also, if you use BP 1.2.8, your buddypress-xx_XX.mo should be in wp-content/languages folder, no more in buddypress/bp-languages