One of the nicer customized Discourse installs I’ve come across: forum.peplink.com 
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It’s not Discourse, but it looks like their design is very heavily influenced by Discourse’s
Interesting topic on their forum: Why did peplink build its own forum?
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They recently reverted back to Discourse. 
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From this topic
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Wow, some people have the luxury of a lot of resources, huh? 
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