Just have sold the WP theme with + 6 month extended support and in invoice stay for customer name - “No name”.
Probably there will be “reversal” and this is not the first time.
I got one customer (before) which still use my theme (and I have access to his admin because I already have done some help with setting up the theme) and have not get money from him because there was “reversal”.
Maybe I am wrong this time, we will see. However, he will still get my theme, like the first one.
I guess reversals are natural for any type of business, so you just have to live with it 
In case you experience such issues, why don’t you license your themes? So you can remotely deactivate them once reversal is made. Sure thing, a person with above average PHP skills will be able to remove this protection from your theme (because theme can’t be obfuscated using ionCube or similar solution), but it will stop a majority of “going to download item and make a chargeback” persons.
Yes, probably you are right.
I am ok for now, there was just 1 until now (on 400 sales) - the last one, with “No name” is still ok (there is no “reversal” for now).
Thank you for your suggestion, I will keep in mind.
Best