I've noticed that with the other music fonts, the bracket's "vertical bar" will expand/contract depending on user-defined size, but it will only do so horizontally. The "tip" portion will sit well on the vertical bar fine enough.
If the user switches to Gonville, and it seems only this font has the problem, the vertical bar will resize horizontally and vertically. This displaces the little 'hooks' and in turn very ugly results can occur. So much so that it detracts from the font's use case. I think Gonville "deserves" to be fixed up a bit having to do with this problem. I can only get it to look decent when the size is really tiny. Here it is mid-sized:
And here it is tiny to get it to sit ok on top of the bar:
I modified my gonville font locally and recompiled it in so that I could achieve something like this:
But it is just a hack (vertical displacement within the font) and it doesn't actually solve the issue of being able to dynamically change the bracket's size well.
Haven't noticed anyone raise this issue, but it should be fixed in the process of these newer "Engraving" activities as per the new forum section etc. P.S. Gonville actually has a pretty decent, generic looking treble clef imo.