The comment formatting section of the editing help pages lists all the available shortcut links you can use in comments, including [help]
for the help center. As of posting that is:
[meta]
– link to the current site's Meta; link text is the site name
(e.g. "Super User Meta"). Does nothing if the site doesn't have (or
already is) a Meta site.
[main]
– like [meta], just the other way around.
[edit]
– link to the edit page for the post the comment is on, i.e.
/posts/{id}/edit. Link text is "edit" (capitalization is respected).
[tag:tagname]
and [meta-tag:tagname]
– link to the given tag's page.
Link text is the name of the tag.meta-tag only works on meta sites.
[help]
, [help/on-topic]
, [help/dont-ask]
, [help/behavior]
and
[meta-help]
– link to frequently visited pages of the help center.
Link text is "help center" (capitalization is respected). All links
point to the main site.
[tour]
– link to the Tour page. Link text is "tour" (capitalization is
respected).
[so]
, [pt.so]
, [su]
, [sf]
, [metase]
, [a51]
, [se]
– link to the given
site. Link text is the site name.
[chat]
– link to the current site's chat site, the link text being
"{site name} Chat".
[ask]
, [answer]
– link to the How to Ask or How to Answer page.
[something.se]
– link to something.stackexchange.com, if that site
exists. Link text is the site name. Use [ubuntu.se]
for Ask Ubuntu.
as remembered from this answer