If that's the only stitch holding the shoulder then it's pretty sketchy yeah. Also look at the lining/pocket stitching - pretty far from legendary JP precision - looks more like DIY job to me.
Scotch guard it first and then wear it hard. Life is too short to baby your gear.
This would definitely work against water, but how about beer or even red wine? Beer is the drink that gets spilled on me the most, which I hate
How often does this happen? I think that we've all gotten a drink spilled on us and it can happen anywhere, but the chances rise when going to densely populated places where people are basically getting hammered. I'm of the opinion of wearing your stuff and not babying it, but if I know that's what's coming I'm not going with my nicest clothes.
Pretty often, as many of the pubs in London get pretty busy, and people are drunk when they go to get their own drinks
John Lofgren Monkey Boots Shinki Horsebuttt - $1,136 The classic monkey boot silhouette in an incredibly rich Shinki russet horse leather. 
Grant Stone Diesel Boot Dark Olive Chromexcel - $395 Goodyear welted, Horween Chromexcel, classic good looks. 
Schott 568 Vandals Jacket - $1,250 The classic Perfecto motorcycle jacket, in a very special limited-edition Schott double rider style. I've done my fair share of pub crawling but in Dublin rather than London, only time pints fell on me were when someone knocked it over accidentally on the table (which often just got me in the trousers as flew through the table and barely on my top) or when the pub turns into a club at night.
Sounds like you should be wearing a raincoat to the places you hang out. I'm not getting scuffed, scratched and drenched when out and about.
