there's a difference in how reddit.com and old.reddit.com format text which comes up a lot with wikipedia links - they use _ to replace spaces, and that's a formatting character, so it gets cancelled by putting a \ before it, which gets messed up somehow in the transfer and ends up as part of the link, so the link breaks
Your link contains a backslash before the underscore in "Fallstreak_hole". This breaks the link in many Reddit clients (including the official Old Reddit).
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u/joemckie 16h ago
https://en.wikipedia.org/wiki/Fallstreak_hole
fixed link