I have thought it was quite unfortunate that all the links using the original URLs for the posts in the old old YaBB-based forum, and even those using one form of the SMF-based forum posts all broke during the forum migration.
Fortunately, we have the Internet Archive Wayback Machine to save us from bit rot!
The Wayback Machine capture of the URL you found is here:
and redirects here:
https://web.archive.org/web/20150124035354/http://forum.arduino.cc/index.php/topic,22105.0.html
I would like to be able to find that post on the current forum instead of using the snapshot. But if you open the forum.arduino.cc URL:
http://forum.arduino.cc/index.php/topic,22105.0.html
You get a 404 page. Even though this URL was translated from the YaBB one by that old_forum_hijack.php redirect, it still is broken because there was yet another change to the format of the forum URLs after that.
Fortunately, the newer SMF format uses the same IDs as the old one so that broken link still provides the essential information that the topic ID is 22105. So I manually translated to the newer SMF forum format:
http://arduino.cc/forum/index.php/topic=22105
Now we finally have a new enough URL that there is a current redirect, which takes us to the Discourse format URL (note that the ID has changed for the third time):