This has been going on for a while.
As stipulated by others here, simply using brackets -- () -- around words will work.
Quotation marks -- "" -- will sometimes be banned though, even if they are in brackets.
Also, even typing the end of the address as you normally would -- example.com -- gets picked up at times.
Try the following: example (at) example (dot) com -- this tends to work for me when buyers want to talk privately.
Or, if you have a website, direct them to that and ask them to use the contact form on your site.