Fix documentation grammar and outdated platform details

Author: sgerbino

doc/modules/ROOT/pages/4.guide/4c.io-context.adoc

@@ -282,17 +282,25 @@ On Windows, the `io_context` uses I/O Completion Ports:
 * Efficient thread pool utilization
 * Native async I/O with zero-copy potential
 
-=== Linux (io_uring) — Planned
+=== Linux (epoll)
 
-Future Linux support will use io_uring for:
+On Linux, the `io_context` uses epoll:
+
+* Scalable to large numbers of file descriptors
+* Edge-triggered notifications
+* Efficient for long-lived connections
+
+==== io_uring — Planned
+
+Future Linux support will add io_uring for:
 
 * Kernel-level async I/O
 * Reduced system calls
 * Support for more operation types
 
-=== macOS (kqueue) — Planned
+=== macOS / FreeBSD (kqueue)
 
-Future macOS support will use kqueue for:
+On macOS and FreeBSD, the `io_context` uses kqueue:
 
 * Efficient event notification
 * File descriptor monitoring

doc/modules/ROOT/pages/4.guide/4e.tcp-acceptor.adoc

@@ -24,7 +24,7 @@ namespace corosio = boost::corosio;
 
 == Overview
 
-An tcp_acceptor binds to a local endpoint and waits for clients to connect:
+A tcp_acceptor binds to a local endpoint and waits for clients to connect:
 
 [source,cpp]
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