For the purpose of identifying [possible] bot-generated usernames.
Suppose you have a username like \"bilbomoothof\" .. it may be nonsense, but it still contains pro
Look up n-gram analysis. It is successfully used to automatically detect text language and works surprisingly well even on very short texts.
The online demo (no longer online) recognized 'bilbomoothof' as English and 'sdfgbhm342r3f' as Nepali. It probably always returns the best match, even if it's a very poor one. I think you could train it to discern between 'pronounceable' and 'random'.