First off, I reported this as a exploit bug via the Anet bug report feature. I tried to explain best I could and gave a screenshot of the spot I saw this occuring. I did not and will not post this to the official forums. I wanted to give our WvW raid leaders a heads up though.
Last night we were fighting in the blue borderland and we had Garrison. Swords popped up on the water gate down on the south-southwest of garrison and I headed over there with my elementalist. Sure enough, Sorrow's Furnace was down there banging on the gate. I got up on the wall to try and defend. However, next thing I know I have a SF guy beating on me, melee range, up on the wall with me. We had a few there and I think the guy got downed or knocked off. But the gate was still up so I was curious how he had gotten up there. We'd held garrison for quite a while so I thought it unlikely that they had a mesmer hidden up there for portals but maybe. But then I noticed something. A small handful of SF guys were on the ledge facing the lake there outside the gate and they started jumping west along the cliff face. And they were trying really hard to jump up on the sloped wall there, near our stairs that lead up to the gate wall. Well a few of us saw them and were trying to hit them with ranged so they did not have any luck getting more in.
This morning I tried to reproduce the steps to bypass the gate (we owned the garrison so I was not trying to do it while another team held it). I was unable to make the jump(s) needed but I'm not too good at jumping puzzles so it may be my skill. I wanted to make sure I wasn't jumping to conclusions (no pun intended) before filing a report. But I went ahead and filed the report with Anet though so they can check it out.
Again, I did not see them successfully make the jumps. But they were for sure inside the outters and roaming and hitting defenders. And it looked very suspicious. Maye we should have quit trying to knock them back and let one jump on up. I have a screenshot and should have taken more I suppose. I think Izzy was up there defending too, not sure if she saw the same thing I did.