https://wordpress.org/support/topic/taxonomy-terms-or-categories-with-commas-within-its-name

rscsv-addon-usecomma.php

<?php
/*
Plugin Name: Really Simple CSV Importer add-on: Comma
Version: 0.1
*/
 
class rscsvimporter_comma {
	// singleton instance
	private static $instance;
	
	public static function instance() {
		if ( isset( self::$instance ) )
			return self::$instance;
		
		self::$instance = new rscsvimporter_comma;
		self::$instance->run_init();
		return self::$instance;
	}
	
	private function __construct() {
		/** Do nothing **/
	}
	
	protected function run_init() {
		add_action( 'init', array( $this, 'add_filter' ) );
	}
	
	public function add_filter() {
		add_filter( 'really_simple_csv_importer_save_tax', array( $this, 'replace_comma'), 10, 3 );
	}
	
	public function replace_comma($tax, $post, $is_update) {
		$_tax = array();
		foreach ($tax as $tax_name => $terms) {
			$_term = array();
			foreach ($terms as $term) {
				$_term[] = str_replace('..', ',', $term);
			}
			$_tax[$tax_name] = $_term;
		}
		return $_tax;
	}
	
}
 
$rscsvimporter_comma = rscsvimporter_comma::instance();