I have created a survey in 2 languages, English and Thai. Problem I am facing is on text response in Thai. When i export or see responses online Thai (any language) is coming as "??????????". English responses are stored properly and able to download properly.
It was not Limesurvey problem, you need to update Mysql table collation to "utf8_general_ci". If you are facing same issue please check your Mysql collation/char set.
Feel free to write back any case of any clarification required.