It seems block elements within inline elements show up as "Multiple unclosed formatting tags" lint error, which is misleading/confusing since the problem isn't actually an unclosed tag, and the solution doesn't involve adding/fixing the closing tag. See en:Template_talk:Infobox_road#Plainlist_in_length_notes and the following section for details, but basically
<br><small>{{plainlist|
*item 1
*item 2
*item 3
}}</small>showed up as "Multiple unclosed formatting tags: <small>". The fix was
<div style='font-size:90%;'>{{plainlist|
*item 1
*item 2
*item 3
}}</div>It would be less confusing if the lint error was something like "Block element nested within inline element: <small>"
Originally reported at en:Wikipedia talk:Linter#Block elements within inline elements.