I suspect people are talking about periods being negative specifically in IM/text message contexts, like Slack, where "send message" has taken over the role of period and period has morphed into an extra signal for something like "finality."

For me, only when used on a single short message sentence. Long explanations and paragraphs get punctuated at usual.

I'll also add I'm not the arbiter of what is and isn't correct or wrong, just explaining my own opinion.