Chain Master link / Joining Link safe?

I have never trusted chain tool joined chains.
The act of removing a rivet from a chain removed the mushroom head area that actually hold the rivet in place. Ergo when you push said rivet back into chain it is missing a crucial part/feature.
Split or joining links should be much safer on a fixed gear bike than they are on freewheel or geared bikes due to the drivetrain always (give or take a split second between pedalling and resisting) being under tension. It is tension which holds these links togother.

Agree with the logic and guess I must have just had a weak split link thing. Never broken a chain that I have joined with a chain tool though, and while it is missing the mushroom bit the rivet is in pretty hard isn't it? (hence the tool to push it in)
I am always adding/removing links as gearing changes so having chain tool joined links is inevitable for me, unless I have more than one split links on the chain :-)