Steps to reproduce

In whatever application with comments, like a Maniphest Task:

1. Create a comment pasting F270656
2. Create another comment pasting F270656

What happens

Visual message:

Text:

Action With No Effect
One of your actions has no effect:

Transaction (of type "core:file") has no effect.

Apply remaining actions?

What should happen instead

No weird confirmation message.

Why that happens

It seems this source code generates the "file reference":

https://we.phorge.it/source/phorge/browse/master/src/applications/transactions/editor/PhabricatorApplicationTransactionEditor.php;ac99285c57a06ed5699b69242fd6588edd950112$2288-2291

Probably, if the file is already referenced, it tries to generate another file reference.

Possible solutions? (one of them)

1. Probably, something should ignore this redundant transaction
2. Probably, this transaction should not be generated