Thanks!

What I found in the admin/language code of 1.7.6 is this:

$lang_add['standard'] =                       "Default view";
$lang_add['standard_d'] =                     "Which view should be used as default?";
$lang_add['standard_thread'] =                "Thread view";
$lang_add['standard_board'] =                 "Board view";
$lang_add['standard_mix'] =                   "Mix view";


I don't know if that's what I was looking for. However:

Oh! OH! I just found out that if I display the forum in FORUM-TABLE view, then a thread or post is always opened in POST-THREAD view. When displaying a forum in FORUM-THREAD view, it always opens a single post only.

This will take some getting used to the FORUM-TABLE view (instead of FORUM-THREAD view) on a forum's page, but it solves my issue with opening a post in thread view by default.