I don't generally chime into these discussions, but would like to put my two bits forward.
Instead of fighting the 'alt abuse' issue, I think we could focus more on the intent of the accounts being used. Regardless of the stats/skills of an account, and whether it's an alt or a main account, or any of those 'tags', we could instead focus on the intent an account is being used for. If someone mines their way close to an enemy deed and then strongwalls/reinforces the account into a 1 tile underground location with no more purpose than to watch who moves around in local, I'd say the intent itself is a toxic one and puts a dampener on overall pvp and play of wurm for most other players.
Whether that strongwalled in account has 20fs, 40fs, 95fs, or 5fs; really doesn't matter in my mind. The account's sole purpose is to put a dampener on the local populations movements and playstyle. The reduction of this sort of playstyle would likely increase the overall enjoyment of a pvp server for the majority of players on it.
Generally if there's an instance of toxic gameplay on freedom, which results in griefing tickets, the wurm team takes all circumstances into view and usually figures out whether there is intent behind the negative gameplay and who/what is going on and takes things from there.
I'd say the same mindset should be used on the pvp side; if you're intentionally playing in such a way to disrupt and/or make the gameplay toxic to others, it should be looked at. I know and understand there are very few rules on the pvp server past personal attacks and such in chat, but there's also precedent when things are taken too far, and usually there ends up being a mechanics change or simply an order to stop doing certain things that are decided to be detrimental to overall gameplay and the health of Wurm itself.
We want this game to be around for a long time, even the argumentative folk usually speak out because they love Wurm and want it to get better. Why can't we police ourselves when we can usually see something as admittedly bad for the game and just stop doing them? Whether mechanics allow or not?
If you look at something and wonder if it should be done, usually it shouldn't...regardless of mechanics. I'd like to extend the idea that it's more fun to play for everyone when it doesn't get nasty and personal on either side. Kill each other, good fight, move on for the next fight.