Question

How to disable space in user name during user registration in Q2A site

Answer 1

You can do it very easily. 

Add this following code at qa-include/plugins/qa-filter-basic.php:51 

Than save the page and you will be done..

if (preg_match('/\\s/', $handle)) {

    return qa_lang_sub('users/handle_has_bad', 'space');

}