Below are the 14 "{{tag}} examples" given in the template's /doc subpage. They show the renderings are unchanged from the modified code, except for the intended change proposed by the edit request. It involves the "hidden comment code", currently rendering as <!--comment--> and modified to render as <!-- comment --> which is in line with the actual rendering that occurs when hidden comments are used.

Markup Renders as
{{Tag|ref}}

<ref>...</ref>

{{Tag/sandbox|ref}}

<ref>...</ref>

Markup Renders as
{{Tag|ref|content=}}

<ref></ref>

{{Tag/sandbox|ref|content=}}

<ref></ref>

Markup Renders as
{{Tag|ref|content=hello}}

<ref>hello</ref>

{{Tag/sandbox|ref|content=hello}}

<ref>hello</ref>

Markup Renders as
{{Tag|span|content=foo}}

<span>foo</span>

{{Tag/sandbox|span|content=foo}}

<span>foo</span>

Markup Renders as
{{Tag|span|open}}

<span>

{{Tag/sandbox|span|open}}

<span>

Markup Renders as
{{Tag|span|open|content=hello}}

<span>hello

{{Tag/sandbox|span|open|content=hello}}

<span>hello

Markup Renders as
{{Tag|span|close|content=hello}}

hello</span>

{{Tag/sandbox|span|close|content=hello}}

hello</span>

Markup Renders as
{{Tag|span|pair|content=hello}}

<span>hello</span>

{{Tag/sandbox|span|pair|content=hello}}

<span>hello</span>

Markup Renders as
{{Tag|ref|open|params=group="note"}}

<ref group="note">

{{Tag/sandbox|ref|open|params=group="note"}}

<ref group="note">

Markup Renders as
{{Tag|references|single}}

<references />

{{Tag/sandbox|references|single}}

<references />

Markup Renders as
{{Tag|br|single}}

<br />

{{Tag/sandbox|br|single}}

<br />

Markup Renders as
{{Tag|!--|content=comment}}

<!--comment-->

{{Tag/sandbox|!--|content=comment}}

<!-- comment -->

Markup Renders as
{{Tag|math|params=chem}}

<math chem>...</math>

{{Tag/sandbox|math|params=chem}}

<math chem>...</math>

Markup Renders as
{{Tag|a|params=href="<nowiki>https://en.wikipedia.org/</nowiki>"|content=English Wikipedia}}

<a href="https://en.wikipedia.org/">English Wikipedia</a>

{{Tag/sandbox|a|params=href="<nowiki>https://en.wikipedia.org/</nowiki>"|content=English Wikipedia}}

<a href="https://en.wikipedia.org/">English Wikipedia</a>


Testing |link=

edit

Valid example:

Markup Renders as
{{Tag|del|link=y}}

<del>...</del>

{{Tag/sandbox|del|link=y}}

<del>...</del>

Invalid example, e.g. of arbitrary XML (it will just go to the HTML element page with an invalid #foo anchor):

Markup Renders as
{{Tag|foo|link=true}}

<foo>...</foo>

{{Tag/sandbox|foo|link=true}}

<foo>...</foo>