More from my actual scientist friend..
“There have been decades of research on the wearing of normal face masks and the evidence is not strong at all. Most of the studies show a positive, but not statistically significant response. Some claim a significant response of about 3-5%, hence the government's line of a "weak but positive effect". Even with those that claim a positive effect, its in symptomatic people (i.e. people giving off large droplets). There is a reason governments, WHO etc were not advising the wearing of masks. But now we need to exit lockdown, suddenly its a must”
I know it’s a bit ‘my friend who knows better than your friend’ but as someone actually working researching this virus (and who has had it, but caught from his wife rather than at work) it takes some beating as a source for me.