When someone asks me, "do you mind if I do this?" and I don't mind I usually respond, "yes" as in "yes, you may" but if my stepdad hears that he thinks I mean, "yes, I mind" and spends some time explaining grammar to me. I still say "yes" meaning "yes, you may" and ask "can I..." instead of "may I..." and most people seem to treat these as interchangeable.
However, more relating to your thread is people taking things out of context. Whether it's the context of the situation or the context of thoughts, if it's not clear to people they will tend to make assumptions, whether correct or, more often than not, incorrect, and will judge what you say based on their own assumptions.
Where they go from there is based on their personal knowledge of you and can lead to practically anywhere: arguments, one person in love while the other isn't, loss of job, depression - all due to miscommunication.