Is it normal to hide your fighting abilities in front of people? For example, I don't let my enemies(bullies) know my abilities and pretend to be weak. Do you encourage hiding your abilities in front of thugs?
IMVHO this seems to be a contrived question, but let's break it down.
Is it normal to hide your fighting abilities in front of people?
Let me turn that question around: how exactly would you exhibit your fighting abilities? And if you exhibit those abilities:
- do you really have them, or do you have an inflated opinion of your abilities?
- what purpose do you achieve by exhibiting them?
The first answer might seem provocative but it is important - if you have an inflated view of your own abilities and you flaunt it then you could get yourself into a pile of trouble very quickly. This is also known as talking the talk but can't walk the walk.
The second question is equally important. If you have no need to show off then don't do so. In fact many styles and instructors will actively guide their students to avoid posturing (or "flexing" as the kids call it) because it achieves very little except to get others to dislike you. Real life is not like the movies, showing off or flexing is unlikely to win you many friends.
The general theme of your recent questions has been how to deal with "thugs". If you are well practiced and actually know what you are doing then you will have a certain body language, a certain amount of assertiveness, and (most) others will pick up on this an not bother you ("thugs" tend to target people who are perceivably weaker). There is no need to highlight this, it is already there. Having said that, if you find that you are still being targeted or bothered then follow the golden rule: don't be there.
So, following that up:
Do you encourage hiding your abilities in front of thugs?
No, because once again that encourages artificially changing your behavior in front of others. I don't flaunt my skills in front of thugs, but nor do I hide them. Pretending to be weak achieves nothing, and acting tough is likely to inflame a situation. Be yourself, nothing more and nothing less.
But most importantly, stop hanging out with "thugs".
No, definitely not!
People who make the first attack on the streets are what is usually called a predator in self-defense.
These kinds of people, like predators in the animal realm, pick their fights carefully. They will only attack as long as they are either sure of their success or desperate. And they will rather retreat than risk serious injury if they realise they misjudged the situation. That is why they often attack out of a group since that makes them feel stronger.
Accordingly, it is not a good idea to appear weak, as this will raise the chances you are going to be picked.
And in all seriousness, because you can never know which abilities or means (weapons) your opponent has, and due to the chaotic nature of a real fight, nobody should ever risk a fight where it can be avoided, even if they are the most capable fighters. You have to look strong and confident. Always. This is the psychological aspect. On the other hand, there are legal and strategic considerations to be made.
As for legal matters, it is important that you do not look aggressive. As long as you keep your cool, take a defensive stance, and do not attack first, you can be pretty sure that you will not face assault charges at the end of the day. Never be the aggressor, even if it would help to pre-emptively intimidate a predator all too sure of themselves.
As for strategic matters, I would always recommend taking a neutral stance that does not disclose your MA background too openly: natural stance with shoulder width, hands open and to the front. The reason is that even if most of the thugs will be hotheads without extensive training, a seasoned fighter can read your stance and eg. tell if you are a boxer only or can grapple or kick as well. That can potentially allow them to know your weaknesses before anything happened.
Apart from that, if you cannot avoid a fight, it is imperative you do show the full extent of your capabilities, as the only thing that can stop the fight fast now is showing them they have made a mistake and will regret any further engagement. Do not corner them by going after them, ever (see the "desperation" part above). But as long as they keep coming, use all your arsenal, which includes "dirty" means like tearing ears, biting, scratching, etc. There is a reason why self-defense instructors emphasize that you should fight like "a madman" or "a dragon", ie. like someone they just cannot overcome. Deterrence is what you aim for, thus holding back does not make any sense at the moment a fight was started by them.
Generally, weakness is the one thing you should never ever show, even if you sustain serious injuries during a fight.