After all this effort in trying to be ultra-precautious, now this: https://www.reddit.com/r/Bitcoin/comments/6qk64y/fired_up_electrum_idly_clicked_on_console_got_this/ and this: https://cointelegraph.com/news/bitcoin-wallets-trezor-electrum-issue-contradictory-statements-regarding-bitcoin-cash

Bitcoin Cash servers in Electrum! "From the official team who are managing Electrum, someone has taken the source code on GitHub and altered it to support Bitcoin Cash." Apparently, as reassurance, Electrum won't recognise Bitcoin Cash headers after the fork. On Reddit Etmetm posted this advice: "This is not a problem. Electrum 2.9 has fork detection and this cash node will not work after the fork as the headers will be refused ... Even pre-2.9 will refuse the headers of Bitcoin Cash (once difficulty is adjusted prematurely), so nothing to worry about ... In fact the author of electrumx (the most widely used server backend) has also implemented quick splitting, so the cash nodes should not appear in the server list of electrum much longer after the fork ... If you've manually connected to a node running bitcoin-abc (Bitcoin Cash) it should not accept your transaction and show an error. You'd then need to connect to a different server. Auto-connect will not keep you connected to a bitcoin-abc node post fork as the headers don't match up."

To be on the safe side, if that's possible, I'm going to manually connect to a non-Bitcoin Cash server from now on with my pre-2.9 wallet. Maybe this should be the focus of a new thread. And here's a warning to avoid installing the Electron Cash wallet on the same computer as your Electrum wallet: https://twitter.com/electrumwallet/status/891935330235973633 ... and the latest Electrum instructions on how to redeem Bitcoin Cash - July 31st: https://electrum.org/bcc2.txt ... it seems that you can safely use your seed in Electron Cash if you follow these instructions.