Hi, The fix for https://issues.apache.org/jira/browse/LOG4J2-3230 looks like it disables recursive interpolation for strings that are not sourced from the log4j configuration. I'm wondering why recursive interpolation is desirable at all, at least as a default? Is it so you can have your config do something like $${env:VARNAME} and let the operator specify a pattern in VARNAME?
Assuming recursive interpolation is useful at all, is deeply nested recursive interpolation useful? Could it make sense to limit recursion to a few levels (e.g. 3 or 5) by default, and let users raise that limit via system property if they really need it? I can't think of a case where you would want deep nesting, but maybe there's a use case? Sorry if this is well-trodden ground, I'm just having a hard time understanding why this feature exists in its current form.
