Most probably someone reports a post from your profile. Doesn't matter if the post made back three years or more either post merited or not, if the moderators think that's spam means they would delete your posts. I believe you have gotten ban due to a massive report. Just getting merit on the post actually doesn't prove that post is a quality post. Because merit would manipulate or send by mistakes as well. Nothing going to change by arguments, just behaves yourself for the future and try to contribute to the forum.