This is me.
Guilty as charged. 
Wow, I have 277 posts in one thread (and I never even opened the “A” thread; what was that about, anyway? - see, lots of things I don’t know).
… you marry a Doper.
BWAHAHAHAHAHAHAHA! You know you’re hardcore when you know just where to go to get some yuks!
… and you consider the name “Cecilia” if it’s a girl…
Robin
When you start using board jargon in your everyday IRL conversations, especially when you never used them previously. I find myself now frequenting words/phrases like “YMMV,” “I pit thee, (fill in the blank)!” and “asshat.” Asshat is just so useful in so many situations…
When you forward every thread about a particular of English grammar to your college English grammar professor, 'cause she finds the discourse to be absolutely fascinating, as do you.
When you have become the Jedi Master of alt+tab to switch program screens, lest you be caught reading the Dope at work!
No, they said “hardcore”, Vix. That should read"
…you marry a Doper who lives on the opposite coast of the US.
[sub](Or in a completely different country, for Coldy and Heloise. Bastard, always having to outdo everyone! 
)[/sub]
Hardcore? That’s when you have non-simulated sex with another Doper on camera.
Oh, and that Alt-TAB thing? It doesn’t work so well if you have 3 or 4 windows open on different areas of the SDMB. 
And Shib? Truly, I admire your courage. That being said, and with all due respect, the REAL hardcore doper is the one who invented Straight Dope Jeopardy in the first place. 
You read page 6 of a thread, to see if somebody replied to something you posted on page 1.
You’re on “final warning” status in GQ.
In your haste to get back to the keyboard, you grab a warm beer instead of a cold one. I just did that.
Your new sig line is: Overheard at the mall: “…and I was, like, Oh…Em…Gee.”
• Your macro program has built-in macros that insert StartQuote and EndQuote brackets so you don’t have to type them.
• Ditto for StartBold, EndBold, StartItalic, EndItalic, etc., for those times when clicking the formatting icons isn’t the way to go
• Your choice of browsers is heavily determined by an ability to open links in the background, and to remain responsive while loading 25 windows simultaneously
You hold up a bank with a 1920’s style “Death Ray” in order to pay the subscription fee.
When having an interesting conversation IRL, you wonder what the folks at the SDMB would have to say about it, and begin mentally composing your OP.
Or you think of an interesting OP, then dissect into a million pieces thiking about what other dopers would say, and decide not to post at all, realizing you would look like an idiot. Thanks to all my fellow Dopers for the mental gymnastics.
Or when losing an argument, you wish you had some Dopers to back you up!
Luckily, my S.O. also frequents a particular message board, so we have had many many conversations that start with “Today on the message board…” and we don’t have to explain what we mean anymore.
As I just discovered, when you absently-mindedly try to italicise something in Word by typing the vB code tag.
You start referring to yourself in your mind as your user name here.
Nice one, Shirley.
Things you read on the boards come back to haunt you at the most inopportune times: funerals, board meetings, rectal exams.
Where is this “number of responses” of which you speak?
When you get fired for spending too much time online while at work - and the only thing you’re on all that time is SDMB.
I speak from experience.
WRS
On the page listing the threads in the forum, the second column from the right is “responses.”
I found myself calling upon Og to smash the last person who did that (and who showed me the Mr Digit Hand Puppet). Does that count?