Embedding MediaWiki Disqus widget inside page footer template

Problem

I'd like to show the MediaWiki Disqus widget at the bottom of each page. And I don't want to edit each page manually.

Solution

Embed the Disqus widget inside templates and use the ReplaceText extension to add a template to the bottom of each page.

Following the steps underneath, each MediaWiki article will now render this:

+----------------+         +---------------------+          +--------------------+         +---------------+
| Article        |     ,-->| Template:PageFooter |      ,-->| Template:Disqus    |     ,-->| Widget:DISQUS |
+----------------+    /    +---------------------+     /    +--------------------+    /    +---------------+
| ...            |   /     | ...                 |    /     | ...                |   /     | ...           |
| {{PageFooter}} +--'      | ==Comments==        |   /      | {{#widget:DISQUS}} +--'      +---------------+
+----------------+         | {{Disqus}}          +--'       +--------------------+  
                           +---------------------+

Steps

#1. Embed DISQUS widget within Disqus template
#2. Embed Disqus template within PageFooter template
#3. Add PageFooter template to each page
#4. (optional) Conditional embedding of Disqus template

1. Embed DISQUS widget within Disqus template

Create a MediaWiki Template:Disqus in which to embed the {{#widget:DISQUS}} widget (replace "yourid"):

<noinclude>This template adds the [http://www.mediawikiwidgets.org/DISQUS DISQUS widget] to an article page.
</noinclude><includeonly>==Comments==

{{#widget:DISQUS
|id=yourid
|uniqid={{PAGENAME}}
|url={{fullurl:{{PAGENAME}}}}
}}</includeonly>

2. Embed Disqus template within PageFooter template

Create a MediaWiki Template:PageFooter in which to embed the Disqus template:

<noinclude>Header at the bottom of each page
</noinclude><includeonly>{{Disqus}}</includeonly>

3. Add PageFooter template to each page

Install the ReplaceText extension, go to page Special:ReplaceText and insert the PageFooter template at the end of each page, using these settings:

field	value	comment
Original text:	`$`	Denotes the end of the text (regular expression syntax)
Replacement text:	↵ ↵ `{{PageFooter}}`	Make sure the replacement text starts with two empty lines. This will insert the `{{PageFooter}}` template on a separate line, making the template insensitive for MediaWiki nested formatting bugs (e.g. `:text==header==`)
Use regular expressions	`yes`

4. (optional) Conditional embedding of Disqus template

Install the ParserFunctions extension, and modify Template:PageFooter like this:

<noinclude>Header at the bottom of each page
</noinclude><includeonly>{{#switch: {{FULLPAGENAME}}
 | Main Page =
 | #default = ==Comments==
{{Disqus}}
}}
</includeonly>

This will make the Disqus template show on every page, except the Main Page.