I was in Spain on July 19th, virtually the day they introduced the law wearing masks almost everywhere excepting beaches, smoking, eating and drinking. There didn’t seem to be any exemptions and police picked you up - to be very fair in a nice way - if you weren’t wearing one and told you to wear it. I know correlation does not equal causation but, have a look at Spain’s figures to see how well this strategy suppressed the virus.
The problem with such tales is that we don't know how it would have panned out without masks, as it could have been a bit worse.
We also don't know how well people were adhering to the other rules which are much better at suppressing the virus. As if keeping your distance isn't being observed then masks would gain you little, conversely it's likely that if you spend a little bit longer than you should or are a little bit closer than a mask is likely to give you a little bit of a better chance of not getting it.
As if you're at 1.5m rather than 2m wearing a mask is likely to mean that less breath gets spread between the two than would otherwise be the case (there is evidence that signing/shouting is more effective at spreading the virus than talking as you project your voice you project air further and in larger volumes, therefore anything which results in the reverse of that is likely to contain the range of your air and the amount of virus in the air near others).
Whilst wearing a mask when exhaling a lung full of vape smoke dose show leakage around the edges of masks it would be interesting to know if that smoke then has the range that it would otherwise have. As I've said before try blowing a candle out whilst wearing a mask and I'd guess that it's much harder than when you're not wearing a mask as you wouldn't be able to get the force behind it.
Now blowing a candle out is a distinct thing and few should be doing something similar when facing others, however coughing or sneezing could be as bad if not worse. Now whilst coughing or sneezing into a tissue would be better that's not always possible (for instance something irritates your nose causing you to sneeze) and catching it in the crock of your elbow isn't going to cover your mouth and nose as well as a mask (obviously best practice would be to replace said mask as soon as possible).
I'd go as far as suggesting that whilst sneezing isn't a Covid-19 symptom that many locations would advise that those who are unwell (so have sneezing as a symptom, rather than a response to their environment) should avoid going there. For example many work places advise not going into work if your are unwell at all (whilst that doesn't necessarily apply to going shopping, especially for getting food, it should limit the movements and settings which people who are sneezing are in - such as not being on a train on the way to work).
Yes, if there's any benefits from mask wearing is likely to be limited, yes there's going to be masks (especially those which are single layers of fabric) which are likely to perform badly when compared to others (however even in the influenza study the level of protection was such that they were 95% sure that there was some protection when the person was wearing an N95 mask and the patients weren't - which is another variable - in a high viral load area for a long time), yes wearing a mask is going give you virtually zero protection when in a high virus load area for a long time (such as in a medical setting) and won't protect you from catching it via another route (such as would be the case of flu, where you could get it at home from your children). As such the evidence is unlikely to be strong either way.
However unless there's evidence from a trail where the majority are wearing masks, where there's generally not very high viral loads likely, where the time limit is measured in fractions of hours rather than significant fraction of a 24 hour period, where people aren't needing to be in close proximity to people (as would be the case of healthcare workers treating unmasked patients), then I'll carry on with the assumption that there's likely to be some limited benefit and so will wear a mask when requested to do so but may not be overly happy when having to do so in a setting which feels pointless (such as outside). The problem is that such a trail would be inconclusive as the risk of getting enough viral load to be infected would be very low (and quite the opposite problem with citing articles where the level of protection is low as it's looking at medical settings where staff are probably on long shifts treating patients but could also catch it from other settings).
Having said that mask wearing isn't a silver bullet and will only ever likely to provide limited protection in limited circumstances, however such circumstances are likely to many of the situations that many people find themselves in.
As such it's certainly not going to make any difference if you live in a village/small town of nearly 9,000 with a local level of infection of 50 per 100,000 (so about 4 people within that settlement) and your main contact with others during the week is outside of school for 10 minutes at a time whilst being 2m apart.
Conversely a fabric mask, no matter how good, isn't going to stop you getting Covid-19 when working on a Covid-19 ward for 12 hour shifts since March providing close personal care of patients.
However for many who fall within those outer edges, whilst the evidence may well be weak, as long as they are doing good hands washing, mostly keeping more than 2m from others, limiting the total number of people that they meet, have a half decent mark which they change frequently, etc. then wearing a mask at worst will have no detrimental impact on their likelihood of catching Covid-19 and may give them just enough of an edge to stop then from getting it or spreading it when they otherwise could when there was a minor slip up in their or others adhering to the rest of the good practice.
The problem is that those very Pro mark wearing tend to think that it's going to protect them more than it is, whist some who are anti are probably those for whom they have a reason why they find it hard to wear a mask and have been upset by those who are very Pro getting on their high horse about enforcement and/or overstating the level of potential protection.
The problem with such threads as this is that there tend to be few from the middle of the debate (and many of those who look in from that position leave fairly quickly) whilst those from either end have their pet evidence which reinforces their starting point and as such the thread goes around in circles.