The Special:CheckUser page hardcodes '(' and ')' characters in the output. This reduces the ability of a skin to style this and make this content responsive. The two offending elements are the timestamp and roles
e.g.
<li><a href="/wiki/User:DoRD" title="User:DoRD"><bdi>DoRD</bdi></a> <span><span><a href="/wiki/User_talk:DoRD" class="mw-usertoollinks-talk" title="User talk:DoRD">talk</a></span> <span><a href="/wiki/Special:Contributions/DoRD" class="mw-usertoollinks-contribs" title="Special:Contributions/DoRD">contribs</a></span></span>‏‎ <!-- problem 1--> (<a href="/wiki/Wikipedia:Edit_filter" title="Wikipedia:Edit filter">abuse filter editor</a>, <a href="/wiki/Wikipedia:CheckUser" title="Wikipedia:CheckUser">check user</a>, <a href="/wiki/Wikipedia:Oversight" title="Wikipedia:Oversight">oversight</a>, <a href="/wiki/Wikipedia:Administrators" title="Wikipedia:Administrators">administrator</a>) <!-- problem 2--> (Created on 17 December 2009 at 03:32)</li>
The new way of doing this is:
<div class=".mw-changeslist-links">Created on 17 December 2009 at 03:32</div>
The visual effect is the same, but it gives skins more flexibility to style.
https://en.wikipedia.org/wiki/Special:RecentChanges, https://en.wikipedia.org/wiki/Special:Contributions and the history pages do not do this and can be used for guidance.