Might be a bug in Parsoid, don't know.
Basic test case is https://www.mediawiki.org/w/index.php?title=Talk:Sandbox&workflow=050c89c8272c23bf2b5f90b11c2788f0#flow-post-050c89c8273423bf2b5f90b11c2788f0
[[User:Foo (disambig)|]] --> Foo (works as expected)
[[User:Foo|]] --> User:Foo (expected: Foo)
Version: unspecified
Severity: normal
URL: https://www.mediawiki.org/w/index.php?title=Talk:Sandbox&workflow=050c89c8272c23bf2b5f90b11c2788f0#flow-post-050c89c8273423bf2b5f90b11c2788f0