This is an interesting feature for small WMF wikis and external sites, but would confuse users on wikis with well equipped user guidance (e.g. English or German Wikipedia).
* Most confusing are two offers, which might happen in German Wikipedia right now.
* Local pages often provide local policies (deletion!) and specific links to related project pages which cannot be achieved with a world wide non-WMF general explanation.
* https://www.wikidata.org/wiki/Q395887 shows present local support just for one issue. I count 60 existing local pages. (The 61st would be: mw:Help:Moving_a_page)

Local confguration needs more emphasis.
* At least a system message should be taken into account by the implementation.
* Icons might be cultural dependant (CJK, arabic, hebrew) and should be configurable per system message – a greek question mark is a semicolon.

Rather than maintaining system messages for each page by each project, a wikifarm with a wikibase could make use of that knowledge. (Okay, WMF might be the only one, but is among the top ten websites)

I would like to see in CommonSettings.php something like
  $wgHelpPages = array()
That may be used explicitly to hard-code page links by any other site.

However, one entry could look like
  $wgHelpPages['special-movepage']['item'] = 395887;

For performance reasons evaluation of the wikibase item is probably not desirable each time a special page is requested by readers.
* Every 24h or once a week that array might be populated and refreshed like:
```
  lang=php
  $wgHelpPages['special-movepage']['pages'] = array(
            'alswiki' => 'Hilfe:Artikel verschieben',
            'dewiki' => 'Hilfe:Seite verschieben',
            'enwiki' => 'Wikipedia:Moving a page',
            ...
```
* Time scheduling and triggering the update might be controlled by something like
```
  $wgHelpPages['UpdateInterval'] = 24;
```
* The same entries might be provided manually by external sites which happen to have their own guidance, but no wikibase and no update service.
I wonder whether the entire helppage link business should stay in core or should be turned into an extension.
* A (help/any) page mapping and linking mechanism might be used in many fields, not only with special pages.
* Various configurations done with system message today might migrate towards wikibase in the future.
* The MW TemplateData gadget e.g. could be equipped by https://www.wikidata.org/wiki/Q14505594 rather than [[MediaWiki:templatedata-helplink-target]].