Should read-only text appear as plain text or in a read-only textbox?

Should I use labels for read-only information, or should I use read-only text boxes to maintain the look of the fields?

It seems to me that if something is in a textbox it implies there is some way to edit it, whereas plain text is explicitly read-only.

Update: While my question is similar to Locking input form fields, does it make sense?, mine is different in that I'm referring to fields that are never editable by anyone. It's not based on the user's rights or role.

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