Is it possible to have my account perma chat restricted?

The goal is to reform your behavior, not prevent the behavior entirely.

You can bind the Chat Button to something Strange so you forget, but Riot doesn't do perma chatrestrictions anymore since it failed last time.

Riot has already tried using permanent/indefinitely stacking Chat Restrictions as a form of punishment, and in the majority of cases, most players under the longer-level Chat Restrictions resorted to gameplay toxicity (trolling, intentional feeding, etc.) to spite their teammates.

Besides - you seem to clearly understand your problem, that's the first step towards fixing it. So, rather than ask for the easy way out, why not actually work towards fixing it for your own betterment, if not that of the people you play with?

Just unbind your "enter" key from opening the chat.

There was one guy who started developing an app for this, idk if he succeeded.

Actually I wrote one too for fun (it simply prevents you hitting enter in LoL, for in any other app your enter works), if you or more players are interested I will release it soon after clearing up the GUI a bit.

Ps.: Assuming you are on Windows.

If you can't stop typing that's fine. Type away. Make sure that the things you type are all nice and constructive and you will get lots of honors for being all friendly and huggable.

I know someone who didnt like the pressure of their honor flair asked riot for a chat restriction once to make it go away. So maybe you could email riot support and ask?

And do you mean a chat restriction where you can only send a few messages a game or one where you can't type at all? I know from asking that they won't completely take away your ability to type. However I haven't yet tried asking for a perma restriction where you can only type a few messages. Might email them later today and will let you know what they say