will only apply up the chain
Should this "up the chain" be "down the chain"?
In terms of a tree, I think of the caller/consumer/thing that imports this file as "up" and the things that I call/import as "down".
That is more consistent with a tree, but not a stack trace (or any stack), I suppose, which has most recently called thing at the top ("up"), and the consumer of that at the bottom ("down").
Retagging the HTML/CSS questions to use html-heading seems the right thing to do. For the other uses, I don't have enough grounding in the geographic area to know whether the direction and bearing are replacements for heading. But the tag information for heading should be created and should firmly point at the other tags — at least until it is expunged.
Yet it can be deceivingly difficult to properly encode (user) input
They were talking about output encoding but then switched to input encoding? Did they really mean to say input encoding here?