The problem is you don't know what is in ink and what is in pencil till years after the fact.

A forum I visited way back when, Kuro5hin, no longer exists but there is some snapshots on archive.org but I doubt that anything I wrote there is accessible (or traceable back to me either here of in real life.)

A blog I wrote for a couple of years back around '07 is definitely still online. But again, there is no way to connect it to current me.

TLDR: Be really sure before you put your real life name or identifying info to anything online.