Javelines sticking to most surfaces can lead to sabotages or difficult gameplay generally.
Sabotage?
I totally get where your coming from, but in reality competitive play wouldn't actually be in any trouble, people would still run with meta-mydians and such, its easier to use, the majority of player know how to use common loadouts, and will still win a match no problem.
Having Javelins affect bombs, walls, allies and such is nice, but I doubt someone would go out of there way to troll a competitive battle like that, really the addition would be more for messing around and doing crazy stunts. (Plus I really want to have football match with exploding mines)
Your own ally bombs don't actually hurt you btw (Unless that one that went through my ship was a bug XD), so explosive flails would be of no consequence either.
If you have ever played AC: Black Flag and faced the HMS Fearless & Royal Sovereign you would know that they attack at the same time, trapping you in a box, these kinds of strategies need to be planned and played out to get it to the kind of sync you would need to make yourself combat worthy with "Ropes and Javelins", not the kind of thing the average player would attempt when thy can just get it done faster with a Gatling Gun and Mortar.
As for "Difficult gameplay"
Naaaaaaa... having it stick to a few extra things wont hurt, especially if you plan on doing this sort of thing your captain is most likely prepared with impact bumpers.
As someone who has been killed by my ally intentionally bombing me, yes, they DO hurt you. The main problem with harpoons working like this is in 99% of matches, you're playing non-competitively. You can't build for the 1%-ers. Games dont work like that. In the other 99% of the game, this change to the harpoon would probably result in trolls intentionally shooting the walls and totally screwing you over. It could even happen with non-trolls if they miss a shot, which is just as bad. Too many situations where this causes more problems rather than creating good opportunities. I like the idea in concept, don't get me wrong, but it doesn't work in execution.
Glad to know bombs ally bombs/mines hurt, as i have yet to hit one.
Here's the thing though, if your afraid of having a random player use the mechanic to troll your ship, don't put it on the ship?
I'm not trying to single out the 1%, rather add a mechanic that brings realism as well as many creative uses.
Also, who said it had to attach to everything? (ok maybe i did, but that's besides the point)
You think a javelin would get stuck in the sand dunes? What about the hard cliff faces in the canyon map?
Not all surfaces have to be "Sticky", just the ones that would be realistic, things like light metal sheets, chains of bombs, trees, etc.
Having it stick to EVERYTHING would not only be an annoyance for missing, but also a game-killer, on that we agree.
I feel like this is something that would be totally do-able within the game, but we can all agree it definitely needs to be fleshed out,