what was the question? you’ve mentioned that there was a post about it, but not asked a question?
I remember reading somewhere if the system detects that your .htaccess file is trying to cercumvent the security system, it will be automatically deleted
If you start your own thread with any questions you have, we can more easily help you 
The post was that the .htaccess gets deleted as soon as it is uploaded. No goofy or unusual stuff in it. Just a simple http to https redirect. That’s standard and not violating anything. It used to work in the past. Not hiding anything, no ill intent.
DirectoryIndex default.php
Header set X-Robots-Tag “index, follow”
Header set X-Frame-Options "allow-from "
RewriteEngine On
ErrorDocument 404 https://www.martinbrieger.com/default.php
RewriteCond %{HTTP_HOST} ^mbsoft.nu$ [OR]
RewriteCond %{HTTP_HOST} ^www.mbsoft.nu$
RewriteCond %{QUERY_STRING} ^(.)i=[^&]+(.)$ [NC]
RewriteRule ^(.)$ /$1?%1%2 [R=301,L]
It looks like this uses a Rewrite condition that touches i. I tried this,
But the file is removed.
Do note that InfinityFree is powered by iFastNet, which has the rights to remove files that they deem are harmful or too large. Seemingly, when touching the i variable, this is a harmful thing.
If you wish to continue this debate, discuss further options, or talk about other things, please open a Topic in Hosting Support.
Also, as a last note, Welcome Back to the InfinityFree Forum!