I went through all of the threads that were in your references. Lots more failures than I believed. Below is a list of the posters with a summary of what was in their posts that applied to their foot peg failure. I might have missed a few; but, I listed every instance that I found. Note that many of the posters acknowledged that they had hit a hard object, tipped their bikes over, or had dropped the bike while in motion. Also, those posts that included photos showed fatigue on the fracture surface showing that a crack nucleated and then grew over time with usage. There were a relatively small number of fractures of the aluminum part of the foot peg assembly.
There were also some posts when the posters (Forchetto among them) checked the tightness of their foot peg bolts and found them loose or the torque was low.
Columbo: Witnessed foot peg failure due to bolt fracture
Oddsteven: left foot peg failed acknowledged the bike was dropped several weeks previous
JxnBonnie: foot peg failed
FlyingCelt: Foot peg bolt failed
Thump Bonnie!: Right foot pegbolt failed
gt1jimmie: Foot peg casting broke after hitting solid object
Durbud: Found his bike lying on its side with broken foot peg (probably bumped by a car)
MES: Foot peg broke. Acknowledged that the bolt may have been loose
WaltZ: Foot peg broke. Acknowledged bolt was loose
greyplague: Foot peg broke after bike went down
SpaceCoastRat: Foot peg casting broke when bike tipped over
Lake: Foot peg broke while riding. Photo shows fracture surface that the surface shows evidence of fatigue failure with only about 40% of cross section intact at time of failure.
Bonnie25: Left foot peg broke
Viperject: Right foot peg broke
Chicagobob: Found his foot peg loose. No breakage
Tornado99: Reports foot peg casting broke on his buddy’s T100. Noted that buddy was second owner of the bike.
Tunabreath: Foot peg bolt broke
MeanStreaker: Foot peg broke
Redstickboy: Foot peg bolt broke on cousin’s bike
dr_kedaver: Left foot peg bolt broke. Photos show fracture surface with what appears to be a fatigue fracture with only 10% of cross section intact at the time of final total fracture
extractable: Left foot peg bolt broke
nimravus01: Broke right foot peg bolt. Acknowledged that foot pegs were used replacements
Cruzin1a: Both foot pegs loose when checked
Snook: Foot peg broke after running into a post.
Ready to Ride: Found one foot peg loose after hitting something.
Irish Guy: Found foot peg casting cracked
WaltZ: Found loose right foot peg. When torqued bolt fractured showing only 1/3 bolt cross section intact
Sasper: Broke foot peg after running into a curb
Untold: Foot peg snapped of when he bumped the bike in his garage
Steve Betts: Foot peg broke after tip over. He noticed his wife’s bike had crack in the cast portion
Forchetto: Reported finding both foot peg bolts loose (actually, torque was low)
DinoZ: Broke foot peg due to tip over
Squidsix: Broke left foot peg at clevis joint
Padre: Foot peg broke “Blasted white metal”
BonnieBlack: Foot peg broke. Great close up photos showing fracture surface. Fracture showed evidence of fatigue and corrosion. At failure, only about 10% of cross section was not already fractured due to fatigue.
Kj6itk: Left foot peg bolt broke
Tecpatl4: Broke left foot peg
Blueback: Reported that his left foot peg was torqued low (10-12 Nm vs recommended 27 Nm). Right foot peg was torqued to 20 Nm
Bonnienyc11: Right foot peg broke
Traveler501: Right foot peg torqued to only 8 ft-lb (10.9 Nm)
RICW: Foot peg bolt broke while being torqued to only 20 ft lb (27.1 Nm)
pgreer: Right foot peg bolt broke
nygumbo: Right foot peg bolt broke. Noted that half of fracture surface was rusty (fatigue failure over time)
Reported second foot peg bolt broke at later date.
JesseD: Foot peg broke.
Ocka: Left foot peg broke
DavidR8: Bike tipped over bending the left U-shaped foot peg bracket. Third owner of the bike. Foot peg bolt broke. Photo showed evidence of fatigue failure
UllyssesCale: Multiple right side foot peg breaks due to tip overs while bike is parked
Dicimus: Broke left foot peg bolt
rmglad55: Broke foot peg
tdnathens: Both foot peg bolts found to be loose
UrbanizedOkie: Left foot peg bolt broke
Not of the TriumphRat forum, a blog reported a broken foot peg bolt
dboone: Cast aluminum part of foot peg assembly broke
extractable: Left side foot peg bolt broke
richm: Right foot peg cast aluminum part broke when bike tipped over in garage
bjh1112: Foot peg broke while riding
bonza: Observed right foot peg bolt failure on pal’s. Noted that pal’s bike had been dropped at low speed previously.