Hi Steel,
Those are good suggestions.
Unfortunately Mabinogi's chat system does not have a quick whisper function or PM function. If players can't do it, it'd be harder for bots to do it.
The string search we can do for a web application. There are actually a lot of housing search that you can use though, including the one here -> http://visionshome.guildlaunch.com/custom.php?page_id=113431&gid=103748.
Regrettably it is very difficult for my bot to take string search inputs for the "!sale" command because it actually listens to input using pixels, not string data. The bot does not actually connect to Mabinogi's chat server to be able to listen to string data. It depends on visual cues on what happens around it then reacts to it. If it sees an image that looks like the "!sale" command, it will respond with the output. Think of our bot as someone who does not understand English but it has a list of symbols that commands it to execute a function whenever it sees it.
Potentially, we can make it learn a lot more symbols to recognize all the possible sale searches. But that would be too difficult to predict and it's probably best to use the housing search in game or a web application for filtering .