Using version 6.1.5 from Curse. Searching for quality, e.g. epic gives 0 results.

I took a look at the code (and later found that someone else had already located the issue, see Jaliborc/ItemSearch-1.3#2).

Open Interface\AddOns\Bagnon\libs\LibItemSearch-1.2\LibItemSearch-1.2.lua and go to line 124.
Replace
Lib.Filters.quality = {
with
Lib.Filters.usable = {

That edit works perfectly, thanks!

I'm experiencing this too.

Yeap ever since the latest update I can't search via quality

Same here, highlighting only green items with search syntax does not work since the last update, item level searching works!

Solved