We support forks that gain significant value. It is impossible to fully predict whether we can support a chain in the early stages and we cannot guarantee to be available on the day of the fork. But we commit to our customers that we will always help them preserve value and that as new chains emerge we will help as the value grows.
You could claim your coin from a fork even if we don't support it, because you hold your own keys. But it's complicated, as it would require someone very technical to do it. They'd have to write the coin signing logic for bitcoinjs-lib, and then get their 2 private keys and use that to sign a transaction.