Using Evolve but I think this effects all your xf2 styles, It's easier to explain on desktop pulling the browser width in, When it hits the first break point the sidebar should go under into 2/3 columns. Currently it goes into 1 and look awkward. At the second break point it sorts itself out goes into columns.

Also, setting the wide responsive break point in options doesn't hide the sidebar at that point.

Tracked it down to the xb_forums.less template

@media (max-width: calc(800px + @xf-xbSidebarWidth))

I changed the above to

@media (max-width:@xf-responsiveWide)

That sorted everything out for me. Thought I'd bung it your way and see what you think
It's an oversight on my part. Previously reported, will be corrected properly in the next release. Your fix works though.

Sorry about the trouble!

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