And why is there no way to style this behavior away other than to compromise and otherwise consistent indentation scheme in the HTML?
.adjacent {
display: inline-block;
background-color: green;
}
<div class="adjacent">Hello</div><!--sweet-->
<div class="adjacent">world</div><!--sweet-->
<br /><br />
<div class="adjacent">Hello</div><!--ugh--><div class="adjacent">
  world</div>