Rationale:

The LWG doesn't believe there is any normative difference between the existing wording and what's in the proposed resolution, but the change may make the intent clearer.

Proposed resolution:

Make this paragraph, the Effects clause for setbuf, consistent in wording with the Effects clause for seekoff in paragraph 3 by amending paragraph 1 to indicate the purpose of setbuf:

Original text:

1 Effects: Performs an operation that is defined separately for each class derived from basic_streambuf in this clause (27.7.1.3, 27.8.1.4).

Proposed text:

1 Effects: Influences stream buffering in a way that is defined separately for each class derived from basic_streambuf in this clause (27.7.1.3, 27.8.1.4).

[streambuf.virt.buffer] paragraph 1 is inconsistent with the Effects clause for seekoff.