[blooalien]

My question is; Why did it get down-voted to oblivion, despite it being a normal practice on other posts?

[freedomben]

My guess is usually when I see it, there's at least a single word description with it, such as "dupe" or "see also:"

[LoganDark]

it can be read as "this has already been posted" instead of "prior art" when the latter isn't explicitly specified