So I take it that the extra word wasn't put in there to increase the entropy/strength then? It's just there to tell you what version of Electrum was used to generate the seed?
Right, it doesn't increase the entropy, it's there to make it possible to detect if a seed is valid or not. If you mistype a word during a restore, it can (with a 99.6% probability) detect that your seed is invalid and warn you.
Why would you advise against trying to memorize an Electrum seed?
Because I'm old and forgetful?
Seriously though, I only meant that I think it's foolish to depend
only on your memory to protect your bitcoin funds. I see no problem if you also have it stored (in hard copy) safely.