Added in 1.8.10
/echo [color] [-abcdefghiNlmnqrstNuvwNINS] [color name] [window] <text>
Prints text in the specified window using the specified color (0 to 37).
-a - Prints to the current active window.
-b - Apply beep options.
-c - Indicates [color] is a color name.
-d - TODO
-e - Encloses the line in line separators.
-f - Apply flash options.
-g - Prevents the echo from being logged.
-h - TODO
-iN - Indents the wrapped line by N characters.
-l - Apply highlight options.
-m - This echo should be treated as a normal message.
-n - Prevents the echo from highlighting the window sidebar/channelbar icon.
-q - Don't print if called from a alias using the . prefix.
-r - Apply strip colors/bold/italic/underline options.
-s - Prints to the status/server window associated with current window.
-tN - Apply timestamp prefix options. N is a optional UTC value to use for the timestamp.
-u - Disables using first word as prefix for nick column.
-v - Treats first word as a timestamp.
-wN - if N = 0, replaces emoticon tags in all token except the first one, N = 1, replaces only the first token, N = 2, replaces all tokens.
-IN - Inserts the line at position N in the buffer. (AdiIRC only)
-S - Used with --IN to force the buffer to scroll he number of wrapped lines of the inserted line. (AdiIRC only)
[color] - A numeric color value to use as line color (0 to 37).
[color name] - Used with the -c switch. One of the following: Action, ctcp, highlight, info, info2, invite, join, part, quit, kick, mode, topic, nick, normal, notice, notify, other, own, wallops, whois.
[window] - The target window.
<text> - The text to print.
;Prints 'Hello World!' to current active window. /echo -a Hello World!