It doesn't matter if Jaxx is part of the NYA. Jaxx users still have their private keys. It's not a web wallet like Xapo where users can lose BTC just by holding BTC in the web wallet.
Electrum under default settings is just as unsafe as Jaxx to use after the fork. It doesn't enforce consensus rules and randomly connects to trusted servers. As there is no replay protection, Electrum should be usable for both B2X and BTC after the fork. So you can be replay attacked just the same.
You should be telling people to move their coins to a Core wallet, not Electrum, if you're concerned about people losing BTC.
It does NOT matter if Coinbase here
https://blog.coinbase.com/timeline-and-support-bitcoin-segwit2x-and-bitcoin-gold-eda72525efd states
"Approximately 24–48 hours post fork. Once we have ensured that the blockchains are stable, Coinbase will re-enable Bitcoin and Bitcoin2x sends and receives. Please be careful when sending funds as certain wallets and bitcoin services may refer to the two blockchains differently."
Quite clear the NYA stance.
Here
http://docs.electrum.org/en/latest/hardfork.html it is stated ...."If you own Bitcoins before the fork, a transaction that spends these coins after the fork will, in general, be valid on both chains. This means that you might be spending both coins simultaneously. This is called ‘replay’. To prevent this, you need to move your coins using transactions that differ on both chains.
Fork detection
Electrum (version 2.9 and higher) is able to detect consensus failures between servers (blochchain forks), and lets users select their branch of the fork.
•Electrum will download and validate block headers sent by servers that may follow different branches of a fork in the Bitcoin blockchain. Instead of a linear sequence, block headers are organized in a tree structure. Branching points are located efficiently using binary search. The purpose of MCV is to detect and handle blockchain forks that are invisible to the classical SPV model.
•The desired branch of a blockchain fork can be selected using the network dialog...."
Can you get the huge difference? Here
you anyone can choose the branch and split the coins, otherwise they'll do double spending by barely importing privvy Keys into the to be B2X wallet (or any other wallet that doesn't allow choosing the proper blockchain).
If we don't allow for this sinking deeply in our minds we'll face serious troubles and probably we'll deserve these.
EDIT:
1)Core Wallet does NOT enable splitting in a handy way for non techies
2)Jaxx has a proven history of epic failures
https://vxlabs.com/2017/06/10/extracting-the-jaxx-12-word-wallet-backup-phrase/#update-extract-pinOther info:
https://bitcoin.org/en/alert/2017-10-09-segwit2x-safetyInside....."we recommend a wallet such as GreenAddress, Electrum or TREZOR" no wonders Jaxx is NOT there