Earlier quoted context omitted.
Spammers know to take off the +spammer part.
Also some websites won't let you put + in the address despite it being a valid character per protocol. Crippling email sign ups for one company, astonishing. Fastmail has subdomain addressing. eg. hackernews@myemail.fastmail.com which is a lot harder to detect.
basename-spammerspecificsuffix@yahoo.com
Where basename is user-chosen (and not necessarily related to the real email address), and the suffix has to be registered ahead of time (so a spammer can't just start randomly generating suffixes to avoid filters).