title: What is the reason to parenthesize <Plug> map names?
body: <p>Many plugins make their public mapping interface accessible through <a href="http://vimdoc.sourceforge.net/htmldoc/usr_41.html#using-%3CPlug%3E" rel="noreferrer"><code>&lt;Plug&gt;</code></a> maps. Users can then use these maps as hooks for their own mappings, e.g. <code>:nmap &lt;Leader&gt;fu &lt;Plug&gt;fooPluginUnlinkRootDir</code>.</p>
  
  <p>Recently I have come across some plugins which put their  map names in brackets, e.g.</p>
  
  <ul>
  <li><code>&lt;Plug&gt;(textobj-indent-a)</code> in the <a href="https://github.com/kana/vim-textobj-indent" rel="noreferrer">textobj-indent</a> plugin,</li>
  <li><code>&lt;Plug&gt;(LineJugglerBlankUp)</code> in the <a href="http://www.vim.org/scripts/script.php?script_id=4140" rel="noreferrer">LineJuggler</a> plugin.</li>
  </ul>
  
  <p>This syntax is not documented anywhere in the help files nor do any of the bundled Vim runtime files use it. Nevertheless, these plugins do their job just fine.</p>
  
  <p>What is the motivation for the brackets? Is there any advantage in using them? Should plugin authors be encouraged to follow this practice (as a best practice)?</p>