I often spend more time actually rereading my post than actually typing it out. As if it mattered whether or not I looked like a moron on a forum... but I still believe it gives more credence to your argument if people don't think you are a moron or just someone who doesn't even give a poo poo about their image when they are debating or giving insight.  

Also, my OCD makes me a lot more attentive to punctuation and, as a result, it can sometimes be easy to get lost in the myriad of commas and semicolons that make up my posts.