But back to the important topic at hand: many people, educated and not, do not understand the role of "however" in a sentence. I know people who are sticklers about language, and they use "however" in such a way because they're quickly texting and want to loosen the rules. That's acceptable, and I've probably done that myself. I'm not talking about those people who know the rules enough to break them; I'm talking about people who don't even know the rule, and think it's acceptable to not use a semicolon or to start a new sentence. In fact, that previous sentence is an example of what I'm talking about: I was joining two independent clauses, thus needed a semicolon, not a comma, which is what a lot of people use even when "however" isn't in the picture.
People usually throw independent clauses together with a comma like it's no big deal (btw--an independent clause has a subject, verb, object, complement...basically, it's a complete sentence, not a fragment, not a dependent clause that serves an introductory purpose, etc.).
So back to "however"...here's an example of how people usually treat it:
I want to go to the store, however I have to work.
That is a comma splice! The comma is separating two independent clauses. It should be:
I want to go to the store; however, I have to work.
I want to go to the store. However, I have to work.
Someone just told me that they hate it when people start sentences with "however." However, that's correct, unless it's a fragment. And that sentence I just typed is correct. This is not correct:
Someone just told me that they don't like sentences that start with "however," however it's fine to do that even though it's not stylistically preferable.
So when is it okay to use "however" with a comma? When it's a side comment...example: (I just created another fragment for emphasis, on purpose, in case you wanted to point it out.)
She wanted to organize a trip for 50 people. What she was planning, however, was not feasible.
Commas around "however"?! That's correct, because it's an aside, a break, instead of starting the sentence with "however" or continuing the previous sentence with "but." For instance, I could write the previous two sentences like this:
She wanted to organize a trip for 50 people, but what she was planning was not feasible.
Those are two independent clauses being separated by a conjunction (with a comma before that, because independent clauses require it).
I can understand why students may not know these rules, but professional writers or people who call themselves "experts" and are writing articles or newsletters to promote themselves really should know better. If they don't know, they should have someone check what they're submitting to stem the flow of bad punctuation.