forresti just recently returned from an almost year-long semicolon sabbatical, starting when i replaced all semicolons in a story with commas and it made just as much sense and flowed better, and now, upon my return, i'm quickly realizing why i stopped using them to begin with: they're simply confusing. the two main rules for usage being, one, separating grammatically complex lists, and two, connecting closely related clauses whose meaning might be interpreted differently without that connection.
the first usage is the most intuitive, and has some practical utility. although, it's easy to confuse a complex list of things with a series of linear actions, like "John ran to the car; he jumped into the front seat; he started the engine; &c," when you could just use conjunctions instead. so, when considering the semicolon, you have to have the stylistic judgement to determine if conjunctions are more appropriate. don't get me wrong, i like having options, but i'm kind of stupid, so.
the second usage is the catalyst for my sabbatical: joining two similar independent clauses with a semicolon because they would otherwise be confusing or misunderstood without one is very weird to me. i've not found many examples in my own writing where a semicolon works better than a comma or simply a period. you get into this trap where you think all vaguely related clauses should be joined by a semicolon, and this quickly runs wild. so i think i'm going to stick with the first usage only.
i'm still on an em-dash sabbatical, for a few reasons that i don't want to get into right now. but i've found that em-dash statements do have some real utility, so writing without them has been interesting to say the least, but also a learning experience, like "how do i make this supplemental information flow in a non-confusing way without using an em-dash statement here?" and this has inspired me to get very creative. imposing rules on oneself can lead to amazing creative innovation.