Use professionel VLINE 

---
 sidebar.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- sidebar.c
+++ sidebar.c	2016-07-26 12:32:38.170166748 +0000
@@ -547,6 +547,7 @@ static int draw_divider (int first_row,
 {
   /* Calculate the width of the delimiter in screen cells */
   int delim_len = mutt_strwidth (SidebarDividerChar);
+  int altchar = 0;
 
   if (delim_len < 1)
     return delim_len;
@@ -557,13 +558,19 @@ static int draw_divider (int first_row,
   if (delim_len > SidebarWidth)
     return -1;
 
+  if (delim_len == 1 && strcmp(SidebarDividerChar, "|") == 0)
+    altchar++;
+
   SETCOLOR(MT_COLOR_DIVIDER);
 
   int i;
   for (i = 0; i < num_rows; i++)
   {
     move (first_row + i, SidebarWidth - delim_len);
-    addstr (NONULL(SidebarDividerChar));
+    if (altchar)
+      addch (ACS_VLINE);
+    else
+      addstr (NONULL(SidebarDividerChar));
   }
 
   return delim_len;