Following up on now closed discussion of some things you can do to adjust the new sticky header option.
I did not want the sticky header to use my default background color, so here's the CSS for adjusting the background color of the new Sticky Header.
/*adjusts sticky header to give it white background when not sticky*/
.forum-topic-sticky-header:not(.fixed) {
padding: 0 !important;
background-color: white;
}
/*background color of sticky header when sticky*/
.forum-topic-sticky-header.fixed {
border-bottom: 1px solid #DFDFDF;
background-color: white;
}
For other options, see Dave's Sticky Tips.