Use this code in the patch file. Replace it entirely.

<?xml version="1.0" encoding="utf-8" ?>
<Patch>

<Operation Class="PatchOperationConditional">
<xpath>/Defs/ThingDef[defName = "AIPersonaCore"]/tradeability</xpath>
<match Class="PatchOperationReplace">
<xpath>/Defs/ThingDef[defName = "AIPersonaCore"]/tradeability</xpath>
<value>
<tradeability>All</tradeability>
</value>
</match>
<nomatch Class="PatchOperationAdd">
<xpath>/Defs/ThingDef[defName = "AIPersonaCore"]</xpath>
<value>
<tradeability>All</tradeability>
</value>
</nomatch>
</Operation>

</Patch>

Mlie, feel free to include this or whatever. I don't care :D