Never noticed this before. Compare these:
[[foo|]] [[foo| ]]
Both render as if they were [[foo]], but the first one is replaced by [[foo|foo]] at savetime, while the second one isn't it. Feature or bug?
I'm a bit skeptical about the need to transform pipetricks at savetime. I think a developer once explained it as not wanting third party users of wikitext to have to know the transformation rules, but that sounds pretty flimsy to me.
Steve