I'm a teacher, so errors jump out at me. In casual written conversation (like Internet message boards), I'm not going to be pedantic though. Judging someone's grammar or usage just gets in the way of attending to their message. If I put the conventions of the written language before the meaning, then I miss a chance for meaningful interaction.
The thing is, although I know that many people don't like to recognize it, dialectical differences are not "wrong".
Language has rules, but rules gradually change. That's because the users of a language are what drive the usage. Words get into the dictionary based on frequency of use and duration, not by some big board of brainiacs adding words they think we should use. It's the users of a language, despite level of education, that drive that language over time.
Sometimes lack of punctuation can definitely cause problems with meaning. If you've ever seen the "don't be a psycho, use commas" memes, sentences like "I like cooking my family and my pets" or "Lets eat kids" illustrate why proper use of commas can keep others from misconstruing your intent. Lol
The only exception for me is when someone is bullying others. There was recently a thread here where the OP was making fun of others. Openly laughing at others while misusing the language leaves you open to criticism. In that case, I would point out that if you're trying to be superior then your grammar should reflect your purpose.
Otherwise, it's all good to me, yo.