OK, if the following contains any errors, let me know please.
Qtwebkit (at least 4.6.X) can't handle any URI with its host part containing space character or "%20" or something similar, but if those offending characters are in the path part, everything goes OK.
In GD, the host part of "bword" scheme is completely useless, its host part and path part are altogether sent to "gdlookup" scheme URI as its query item.
Obviously, in GD, "bword" scheme should be non-hierarchical, like "mailto", as explained by
RFC3986, with the whole "location identifier" as its path part.
So, there is a simple solution to that problem: make "bword" the same as "mailto", that is, disable its host part, as the patch does.
Er, it seems I forgot to delete the code handling the host part (now, it's an empty string) of "bword" link in ArticleView::openLink() function, the new patch is in the attachment of this post.