I have created #1639 <https://github.com/apache/logging-log4j2/pull/1639> fixing #1626. There I rewrote `ParameterFormatter`, which is a crucial performance-sensitive core component. *I will appreciate some review from others.*
In a nutshell, given certain input, the earlier version was either throwing `ArrayIndexOutOfBoundsException` or formatting escaped escapes incorrectly. In the meantime, I will adapt the performance tests and make sure that there are no regressions.
