Just to offer an "official" reply from Festool on the matter...
When Festool took ownership of this forum, one of the guiding principles was to keep it open. By that I mean that members can express their feelings, positive or negative, about our products without censorship or retribution. Of course, we do have general guidelines that outline expected decorum, like no cursing, be polite, etc. just to keep the peace here on the forum.
There were posts removed in that thread that suggested a ways to override the mechanics of the Kapex's trenching setting. One of our forum guidelines, which is intended to keep anyone from getting hurt, is that members cannot discuss or demonstrate using a tool in a method not prescribed by the manufacturer or outside of its intended use. We have members of varying levels of skill and tampering with safety controls or modifying the mechanical or electrical systems of a tool could result in personal injury or less importantly damage to the tool. I don't think any of us want that to happen.
That's why the post was removed. It had nothing to do with criticism. As an example, this thread exists and will not be modified or removed even though it is a criticism of Festool and its moderation of this site.
Hopefully, you'll better understand our position on the removal of the post even if you don't agree with it. It's about safety and best practices, not censorship.
Now, about the depth range for the trenching mode... I can tell you that Festool Germany is very attentive to the discussions that take place on this forum, even if they are not participants. Sometimes, feedback from our forum members results in changes to tool designs. Maybe it will in this case, maybe not. But we, Festool that is, appreciate the constructive criticism and suggestions to make our products even better.
Shane