urlhammer

I have a question about posting hidden links in forums,

Lets say I am in a forum that has to do with cars, and I am active within that forum by posting threads and responses that are on average over 150 words and lets say I post an external link by linking a "period, comma" or something within the paragraph that no one will really notice and see.

Will this help me in the search engines or hurt me?

Also if the links are going to say blogger which is owned by google I'm assuming it will not hurt me but I could be wrong. Some advise here would be helpful.

thanks