simple-ajax-chat-form.php
Find this.
$sac_out .= '<span class="sac-chat-name" title="'. sprintf(esc_attr__('Posted %s ago', 'simple-ajax-chat'), sac_time_since($chat_time)) .'">'. $url .' : </span> ';
Change to this and change the link.
$sac_out .= '<span class="sac-chat-name" title="'. sprintf(esc_attr__('Posted %s ago', 'simple-ajax-chat'), sac_time_since($chat_time)) .'"><a href="https://yoursite.com/profile/'. $url .'">'. $url .'</a> : </span> ';
The problem with this chat plugin is when chat is updated live it allways prints plain text. So it wont work when people are chatting live. But will work on NOT LIVE updated message the messages which already are there. Or people refresh the page.
If you want it to work allways even in live updated messages i would sugest Schreikasten plugin which i use. https://www.ads-software.com/plugins/schreikasten/
When new messages comes it actaully updates the whole box so the user links allways works even in LIVE chat.
Anyways i hope i helped you a little.