When I summon an entity with the "Tags:[<tags go here>]" tag, I can test for only one with the brackets syntax (e.g. execute @e[<brackets syntax>]). In case I'm not clear enough, here's an example:
/summon ArmorStand ~ ~ ~

{Tags:["tag1","tag2"],CustomName:Bob12}

/summon ArmorStand ~ ~ ~

{Tags:["tag1"],CustomName:Bob1}

/summon ArmorStand ~ ~ ~

{Tags:["tag2"],CustomName:Bob2}

/say @e[tag=tag1] (-->Bob1 and Bob12)
/say @e[tag=tag2] (-->Bob2 and Bob12)
Here's the interesting part:
/say @e[tag=tag1,tag=tag2] (-->Bob2 and Bob12)
/say @e[tag=tag2,tag=tag1] (-->Bob1 and Bob12)

Clearly it picks the latest tag used and I'm sure this issue falls under the same category as the unability to use multiple "type=" tags and I'm sure that was something we were able to do workarounds for, but this is a new feature and as such I would like to be able to use it 100%.

Thanks for reading this
Patha