Will giving my Chinese friend an endorsement/invitation hurt his chance of getting his visa?

An American consular officer usually wishes to be convinced that there is some purpose to the intended trip. Your endorsement and invitation would probably help rather than damage your friend's ability to obtain a visa to come to the US as long as it also confirms the temporary nature of your friend's trip. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.