I really, really don't get this.
Most people will only 'like' funny threads that will make their friends laugh, very few people are going to link DV or potty training threads. A thread which gets 10 likes will be shared with maybe 1000 people (most of whom won't be interested enough to click the link) as well as the 1.5m MN users.
I know one of my RL FB friends is a MNer because she has bought almost every one of the 'MN swears by' products and often uses MN phrases. I have no idea what her MN user name is, whether she lurks or posts and I am unlikely to find out unless she posts anything really identifiable that I happen to see.
I have clocked a relative on here when she started a thread giving away a bit too much info in the title. Scarier than that after she namechanged I spotted her again from a thread title, a 3 word thread title with no real personal info - most people on here are really surprisingly obvious to anyone who knows them.
If you're worried about people finding out who you are and digging up old threads then complain about the advanced stalk search function. It is way more efficient than trying to google the same info.
I namechange all the time but this is a subject I go on about quite a lot. It's a public board, you only remain anonymous if you make the effort to keep it that way.