Writing is not the same as speaking. Abbreviations are acceptable but confusing abbreviations would be a trouble.
Since "cause" can mean induce or reason, it can confuse the others if they are not able to replace it with another words. It is inconvenient for readers and it is too informal.
Why don't you try to use some clear wordings so that readers will not be confused and frustrated when reading your posts.
I understand it is quite difficult to use formal wordings in writing when you are using informal language in conversion, but it is more difficult for those who are not native English speaker to understand informal language and idioms. So, I advise you to use either Chinese or formal English when writing posts.
Sorry for my poor English but really I hate using the Chinese typing software installed in the school computers.
I agree with your post in#85 and you've got all gramma correct. I think it would not be your problem if that passage is not understood by somebody.
The way I see contractions is that if you want to use a contraction, make sure everyone knows what you mean. HKPNVE is a local HK forum and contractions should be avoided.