Bug#1030119: release-notes: openssh-server: fills the log with "deprecated reading of user environment enabled"

[Laura Smith <n5d9xq3ti233xiyif2vp@protonmail.ch>]

You wanted to "track down an actual reason for this change" ?

Try this:

CVE-2011-3148
CVE-2011-3149

As summarised by Redhat (https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/6.4_technical_notes/pam):

If an application's PAM configuration contained user_readenv=1, a local attacker could use this flaw to cause the application to enter an infinite loop.