Very long ago, when I was young, my teacher once told me that there only should a period “.” or a semicolon ”;” in front of “however”, but never a comma “,”.
To be specific,
“xxx. However, xxx”
”xxx; however, xxx”
is right; whereas,
”xxx, however, xxx”
However, I rarely see such rules in people’s writings even those very formal ones.
The teacher was really knowledgeable that he wouldn’t have said that if that made no sense.
I’m now confused, and I’d appreciate it if any help is given.