I agree, I prefer `SLF4J-API` and `Logback`
 it is causing any harm? maybe we can just mark it as deprecated, comment it will be removed in future releases, and recommend using an alternative (e.g. slf4j).
 > it is causing any harm?

No harm. It is very outdated and not used within netty. Deprecation also fine.
 +1 for deprecated.
 Fixed

Proposal : remove commons logging classes
Remove `CommonsLogger` and `CommonsLoggerFactory` classes.

Commons-logging project is not updated for 2 years already. I propose to remove it also from netty too.

Let me know If I can submit PR.

common/src/main/java/io/netty/util/internal/logging/CommonsLogger.java common/src/main/java/io/netty/util/internal/logging/CommonsLoggerFactory.java
common/src/main/java/io/netty/util/internal/logging/CommonsLogger.java common/src/main/java/io/netty/util/internal/logging/CommonsLoggerFactory.java
diff --git a/common/src/main/java/io/netty/util/internal/logging/CommonsLogger.java b/common/src/main/java/io/netty/util/internal/logging/CommonsLogger.java
index 1068005e893..110f0f1cf92 100644
--- a/common/src/main/java/io/netty/util/internal/logging/CommonsLogger.java
+++ b/common/src/main/java/io/netty/util/internal/logging/CommonsLogger.java
@@ -44,7 +44,11 @@
 /**
  * <a href="http://commons.apache.org/logging/">Apache Commons Logging</a>
  * logger.
+ *
+ * @deprecated Please use {@link Log4J2Logger} or {@link Log4JLogger} or
+ * {@link Slf4JLogger}.
  */
+@Deprecated
 class CommonsLogger extends AbstractInternalLogger {
 
     private static final long serialVersionUID = 8647838678388394885L;
diff --git a/common/src/main/java/io/netty/util/internal/logging/CommonsLoggerFactory.java b/common/src/main/java/io/netty/util/internal/logging/CommonsLoggerFactory.java
index 3e9ab9fafdb..2b4af9f4e9b 100644
--- a/common/src/main/java/io/netty/util/internal/logging/CommonsLoggerFactory.java
+++ b/common/src/main/java/io/netty/util/internal/logging/CommonsLoggerFactory.java
@@ -18,14 +18,15 @@
 
 import org.apache.commons.logging.LogFactory;
 
-import java.util.HashMap;
-import java.util.Map;
-
 /**
  * Logger factory which creates an
  * <a href="http://commons.apache.org/logging/">Apache Commons Logging</a>
  * logger.
+ *
+ * @deprecated Please use {@link Log4J2LoggerFactory} or {@link Log4JLoggerFactory} or
+ * {@link Slf4JLoggerFactory}.
  */
+@Deprecated
 public class CommonsLoggerFactory extends InternalLoggerFactory {
 
     public static final InternalLoggerFactory INSTANCE = new CommonsLoggerFactory();
