Typically Yes.
For SC, per
SOUTH CAROLINA NONPROFIT CORPORATION ACT [emphasis added]:
SECTION 33-31-724. Proxies.
f) Subject to Section 33-31-727 and any express limitation on the proxy's authority appearing on the face of the appointment form,
a corporation is entitled to accept the proxy's vote or other action as that of the member making the appointment. SECTION 33-31-722. Quorum requirements.
SECTION 33-31-722. Quorum requirements.
(a) Unless this chapter, the articles, or bylaws provide for a higher or lower quorum, ten percent of the votes entitled to be cast on a matter must be
represented at a meeting of members to constitute a quorum on that matter.
Hence, if the Corporation is accepts the proxy as representing the members vote, it would be logical to conclude that this member's "represented" vote would be counted toward a quorum.
I will add, that typically a quorum is defined as x percent
of the members, in person or by proxy, entitled to vote.
The SC statute isn't looking at the members, it's just looking at x percent
of the voting interest. Therefore, if one member owned 10 out of 100 lots, that member would equal 10% of the voting interest (expecting 1 vote per lot) and thus satisfy the quorum requirement.
Other States may have different laws, so be sure to check (typically under the applicable corporate statute).