The system appears to have been purposefully used by agency officials responsible for the targeting of conservative non-profits, in order to evade public scrutiny.
The system, known as "Office Communication Server" or OCS was used by IRS officials, including many in the Exempt Organizations (EO) Unit, which was headed by Lois Lerner.
As the Oversight Committee report states, the instant messaging system did not archive any communications, so it is not possible to know what employees of the EO unit discussed on it.
However, in an email uncovered by the Committee Lerner warns her colleagues about evading Congressional oversight:
"I was cautioning folks about email and how we have had several occasions where Congress has asked for emails and there has been an electronic search for responsive emails – so we need to be cautious about what we say in emails."