This is sign language. Sign language, though some think it is simple, is intricate and complex.
The symbols being used here are tentatively thought to mean ‘journey’ ‘lock break/break in/burglar”
This was developed for use in loud forges. Remember the part where all those hammers are ringing in the very beginning? It’s loud as balls. Or when working in a mine, say shoring up the walls when you honestly feel like loud acoustics can damage the structural integrity of your mine. [Trust me, it’s just as possible as a avalanche.] Or say that you don’t know if this new mine has orcs in it, so you can’t be loud. You would use this. While there are different dialects, all dwarves know this.
Bifur is not stupid guys. Thorin would not set out to reclaim his home and add someone who he thought wasn’t smart enough to do what needed to be done just to appease the Ur Family, who aren’t even dwarves of Erebor, they came from Moria. Bifur would not be allowed to come if he was mentally handicapped to the degree that he is being portrayed in the fandom.
My patience with the fandom and disability tropes is wearing thinner than that bridge in Moria. I’ve probably said it a hundred times, but I could have cartwheeled in the theatre when they showed Bifur. Having a character you can relate to that isn’t a sob story, trite superhero or blown out of proportion is such a GREAT feeling…and to come back to a fandom you’ve been in for over a decade only to have that bubble popped by ableist tropes and feeling alienated because you have the same traits that everyone’s criticising…it hurts. It really…fecking hurts.
Signed languages are as complex, beautiful and practical as any other language. Especially in Khuzd culture where the preservation of heritage and cultural identity is SO important…even to the point that their “secret” Khuzdul names aren’t put on their tombs. This preservation only became more important after the Exile (it could be paralled to severl Norse and Romani themes..but that’s another rant.) Signing is NOT a negative thing. Bifur having a means to communicate with his kin after an injury that affected his speech center? That’s a GREAT, COMMUNITY BOND forging thing.
When signing, proximity to the body and facial expressions add just as much meaning as the signs themselves. It looks like he’s signing close to himself, almost intimate. Like a comrade’s whisper, but is face looks eager/intense…so what he’s saying is important. If he indicated at Bilbo the signs could be (He)(sneak)GO + BREAK + LOCK, (He) + BURGLAR. Or if they were discussing not having the key…(he) + PICK + LOCK (sneakysneaky). If that’s true then he has pretty high opinion of Bilbo’s burgling skills from the start and is trying to get the Company just as confident.
Or I’ve had too much coffee and am addled from rage and should just go crawl in a hole now.