That woman was an idiot! The bridges have to stay. I use a blue washable marker with never a bad result. I will mark a red snippet of fabric or sometimes all of the fabrics (just a test snip) with the marker before I start piecing the quilt. After I am done piecing and am ready to mark, I will soak my test snips in COLD water. If all the marks come out, I know it is safe to use on the quilt. I always wash my quilts when I am done, so first I put the quilt in my washer and fill it with COLD water, agitate a bit, then spin. Now you can wash with detergent. If you just wash with detergent first without rinsing with cold water, you might set the marks.