I would appreciate any opinions regarding the members of a proposal review team (we call them the "Buying Team"). This would be specific to best value source selection (BVSS) solicitations. Do you feel it is appropriate for a manager and their direct report to be members of the same Buying Team? Do you think there are conflict of interest concerns? Coercion or undue influence? I look forward to your opinions. Thank you.

We have a policy of no supervisor/subordinate relationships on our technical evaluation panels.  I'm not aware of a requirement in law for that, and I don't think it was an actual problem before.  We make policy by crackpot complaint, though, and that's how that rule was established.  If there is more meaningful guidance on this issue I'd like to hear it as well.  Thanks, sjst1!

If we're being asked whether a supervisor ("manager") can be on an evaluation team with his or her subordinates ("direct report"), then the general answer is yes, unless agency policy forbids. Presumably the OP's concern is that the supervisor might pressure the subordinates to evaluate in a certain way. That might be a legitimate concern in any given case. But think of military agency acquisitions in which the head of the team is a colonel and the members include majors, captains, and lieutenants. They're all subordinate to the colonel. I think that on every source selection that I can remember there were supervisors and subordinates on the same team. I have never known that to be considered a conflict of interest.

The general principle, as expressed by the GAO, is as follows:

Quote

[W]e have long held that the selection of individuals to serve as evaluators is a matter within the discretion of the agency, and, accordingly, we do not review allegations, such as these, concerning the evaluators' qualifications or the composition of evaluation panels absent a showing of possible fraud, conflict of interest, or actual bias on the part of evaluation officials, none of which have been alleged or shown here.

Savvee Consulting, Inc., GAO B-408416.3, 2014 CPD ¶ 92.

You can find the same sentence in more than 100 decisions going back to the 1980s.

Here is one decision that addresses the OP's specific concern, but it's old:

THIS OFFICE HAS CONSISTENTLY HELD THAT THE COMPOSITION OF A TECHNICAL EVALUATION PANELIS WITHIN THE DISCRETION OF THE CONTRACTING AGENCY, AND WE WILL NOT OBJECT IN THE ABSENCE OF EVIDENCE OF FRAUD, BAD FAITH, CONFLICT OF INTEREST, OR ACTUAL BIAS. HSA/MULTICHEM, B-202421, AUGUST 11, 1981, 81-2 CPD 118; NEW YORK UNIVERSITY, B-195792, AUGUST 18, 1980, 80-2 CPD 126. WE DO NOT CONSIDER THE MERE FACT THAT THE TEC DID NOT INCLUDE CALIFORNIA DESERT SPECIALISTS TO BE A PROPER BASIS TO QUESTION THE COMPOSITION OF THE TEC, PARTICULARLY AS THE RECORD SHOWS THAT ALL TEC MEMBERS HAD CONSIDERABLE EXPERTISE IN ARCHAEOLOGY IN GENERAL AND IN THE ADMINISTRATION OF ARCHAEOLOGICAL SERVICE CONTRACTS IN PARTICULAR. WE ALSO DO NOT CONSIDER THE AGENCY'S INCLUSION OF ONE COMMITTEE MEMBER WHO WAS EMPLOYED AS A SUPERVISOR OF OTHER MEMBERS AS EVIDENCE OF BIAS OR CONFLICT OF INTEREST - THERE SIMPLY IS NO EVIDENCE THAT ANY MEMBER OF THE TEC FAILED TO EXERCISE INDEPENDENT JUDGMENT IN HIS OR HER EVALUATION.

Emphasis added. Capitalization in the original. Westec Services, Inc. GAO B-204871, 82-1 CPD  257.