Go to admin panel "Markup" menu, Modify, select quote and /quote:
HTML:
Replace current code with:
<blockquote><font size=1 face="Verdana,Arial,Helvetica">Quote:</font><hr color="#A1A576">

Closing Tag HTML:
Replace current code with:
<hr color="#A1A576"></blockquote>

Repeat for reply] and /reply
optionally replace for Code and Pre


Edit template include_post_html_common_write.html to add a message to user when quoting.

BEFORE
<br><br>
<input type="submit" class="button" name="do=<%this_do%>;basic_editor=1;basic_editor_switch=1" value="Switch to Basic Editor">
<%if current_user_id%>

INSERT
<%if message_quote%>
<%body_font%><font color=red>
When quoting a message, make sure you type your text after the bottom horizontal line or it will be lost.<%/body_font%>
<%endif%>


Add global var in admin panel "Templates" menu, Global Vars, New:

message_quote

sub { $IN->param("quote") and return 1 }