Relevant Product: Exclaimer Cloud - Signatures for Office 365
When you view and collapse email chains in Outlook Web Access (OWA) the signatures don't get hidden and it often appears as if the emails consist of signatures only and no body text.
When an email is viewed in webmail apps, such as Gmail or Outlook Web Access (OWA), the signature and the body of the email are separated into separate 'quoting' areas, and in certain collapsed views, the text of the email body is hidden, but the signature portion is not.
This gives the illusion that the email chain on Gmail or OWA is a chain of signatures with no text body between them.
Please note this is expected behaviour as confirmed by Microsoft.