I'd be interested in seeing some reliable evidence about this.

I sleep fairly poorly, and consequently I've used earplugs nearly every night for 5+ years now. I do have bad tinnitus (it is congenital), but it has not become worse from this. I have not had any ear infections in this period. I've had my hearing checked twice over the past 5 years, and it is stable at all frequencies.

It's worth noting that most earplugs will fall out after an hour or so, or at least the ones I've been using will. I buy a ton of cheap foam ones and rotate them periodically.

The only thing that has made my tinnitus worse best I can tell was a bursting rubber tube, which was basically as loud as a shotgun. This added a specific and identifiable frequency to one of my ears, oddly enough, but had no other long-term effect.