People love giving their characters disabilities, but hate following the rules that go along with the disability.

First of all, in RPs where fighting is common, why would you want a blind or deaf character anyways? This would mean they would be dead almost immediately.

Example

Warrior Cats RPs have a lot of fighting in it. Because of the net of a Clan, it's understandable that cats who are blind can survive. However, they cannot hunt or fight. It's impossible, as portrayed with Jaypaw.

People like to claim their characters can hear movements like Dare Devil or something. This is impossible. If you didn't want the handicap of blindness, you shouldn't of made the character blind.

Phobias, trauma and other mental problems are similarly ignored.

This one is more like ignorance than anything else. People like giving their characters unique problems, but don't do their research about them.

Example

Rose has aquaphobia (fear of drowning, different than hydrophobia). She refuses to get into water that's over 4 ft deep and hates being underneath the water for an extended about of time.

Other people who gave their characters aquaphobia said their character swims and readily got into pools. This is not how they would react.

There are more extreme disorders, such as bipolar and schizophrenia. I would suggest researching these and making sure you're portraying them right.

In short, I dont suggest disabilities for inexperienced roleplayers or those who haven't studied it.