As I was trying to separate normal threads from sticky ones I finally managed to do it and it was very simple. There is no need for template modification whatsoever.
1- Go to template forum_view
2- find this code
<xf:macro template="thread_list_macros" name="item" arg-thread="{$thread}"...
Simple css (extra.less) modifications to highlight/separate sticky threads
Separate sticky and normal threads
Insert code in template: extra.less
/* Border between sticky/normal threads */
.structItemContainer-group--sticky {
border-bottom: 6px solid;
color...
