I was told many years ago that one CO cannot sign a contract "for" another CO. The name in the signature block must match the signature. Is that still correct and where is the requirement for this? Does that apply to all correspondence being signed by the Contracting Officer? I feel this is a legal question.
No, one contracting officer can not sign for another contracting officer. Warrant authority is recieved from an appointing authority with specific instructions regarding the limits of the authority of the warrant. The warrant is given to an individual - usually with limits such as dollar amount and agency organization or program office. That authority is not passed to another individual just because they write "signed for XXX". The Contracting Officer that is signing the document is signing for him or herself, not for the person on the signature block. If one contracting officer goes TDY or on leave, for example, another contracting officer with appropriate authority may have to take over during this absence.
In that case, I recommend changing the signature block. FAR 1.602-1 -- Authority.
(a) Contracting officers have authority to enter into, administer, or terminate contracts and make related determinations and findings. Contracting officers may bind the Government only to the extent of the authority delegated to them. Contracting officers shall receive from the appointing authority (see 1.603-1) clear instructions in writing regarding the limits of their authority. Information on the limits of the contracting officers’ authority shall be readily available to the public and agency personnel.
(b) No contract shall be entered into unless the contracting officer ensures that all requirements of law, executive orders, regulations, and all other applicable procedures, including clearances and approvals, have been met.