The rules of the Russian section prohibit exactly plagiarism, and not copying news headlines.
We have notes under the list of rules and here is one of the note about plagiarism:
Примечания:
8. Плагиат запрещён, в том числе в виде копирования, либо перефразирования чужих сообщений или текстов из сети Интернет. Если выкладываете копипасту, то обязательно указывайте ссылку на источник.
Translation:
Plagiarism is prohibited, including in the form of copying or rephrasing other people’s messages or texts from the Internet. If you are posting something which is copied, you must include a reference to the source.
However, I believe that a temporary ban would be sufficient in this case because there is just one mistake, and he did it not to earn some money from signature campaign or not to raise his activity.