"Convention food" could also be called "event food" or "wedding food" or "catered food" or simply "restaurant food".

there's a huge ignorance about food in general and it gets worse at mass meals.

it's hard to blame the staff because as individuals we know so little about what we eat.

often events are staffed with temporary workers; frequently they may not even speak
English (or whatever language is your mother tongue) well.

occasionally, I've been lucky to get at really awesome dish while the rest of the attendees regretted their own dishes.

sadly, that's not usually the case ... this is often a question of logistics:
it's easier to give everyone the same fare than it is to deal with the exceptions.

for those of us who for whatever personal reasons happen to be among the odd man/woman out group,
we often get served last ... sometimes we get to start our meal as everyone else is finishing theirs.

sometimes we get lucky ... I was a vegetarian for quite a while
and enjoyed jellied pineapple that my late mother in law used
to prepare ... one day it clicked with father in law that jello is
from gelatin which is from the bones of animals ... years later
at an event catered by the Toronto Board of Trade, I was
served a salad while everyone else had a meat dish ... unfortunately,
the salad came covered with lumps of jello ... the staff took it away
and brought me a salad without the jello ... the good part was that the maitre d'
knew quite a bit about food (his passion) and told me about a seaweed
substitute for gelatin:  agar agar (http://en.wikipedia.org/wiki/Agar).

we also need to be careful about changes to ingredients ... whatever it is that you are trying to avoid,
you are in a position where you must always recheck the ingredients ... example, I have often
eaten "licorice babies" from our Bulk Barn chain ... the Bulk Barn lists the ingredients
of each product on every bin ... recently, Bulk Barn "licorice babies" started to include gelatin as an ingredient.

Toronto has "fresh", a great chain of vegetarian restaurants ... "fresh" uses peanut
based products for one of its toppings ... sadly, that takes "fresh" off the map for people with peanut allergies.

Many restaurants have books you can see to check out the ingredients;
in some cases, that book can be three or more inches thick if the restaurant has a lot of menu choices.

Chinese restaurants can take certain ingredients for granted, example:  oyster sauce.
again, the language barrier is a problem.

A friend of mine can die from eating fish or seafood.  He was ate the appetizer bread at
Mother's Pizza and his throat started to close up ~~ turned out that Mother's Pizza was using "butter" may from "fish oil".

There's only one really safe solution:  eat prior to or after the event and/or bring your own food.

While speaking to the chef in advance is essential, frequently it's like have a conversation with a brick wall.
If the chef does not screw up your special meal, her/his staff are likely to do just that.

Even eating in your own home can be unsafe:  "sulphur dioxide is widely used as a commercial preservative of vegetables,
 particularly of greens" ~~ this is a problem for people allergic to sulphur dioxide.  http://allergyadvisor.com/example.htm.

regards,
gerry (lowry)