Firefox running with rare arguments
Solution 1:
Probably not removable, but that will appear only when browsing web pages.
What is that line of argument
When running Firefox 54 or newer release, the Multiprocess Firefox (a.k.a. Electrolysis or e10s) is now enabled by default for all users. The latter link has explanation for the matter on MozillaWiki.
Electrolysis functionality hosts, renders, or executes web related content in background child processes which communicate with the "parent" Firefox browser via various ipdl protocols.
So the line of argument -contentproc -childID 1 -isForBrowser [...] appears in process list because Firefox is running with multiprocess enabled by default.
The cryptic part of argument ¼½¾ǃː̷̸։֊׃״؉؊٪۔܁܂܃܄ᅟᅠ᜵ [...] seems to correspond to the blacklisted characters by Mozilla, as per network.IDN.blacklist_chars documentation at MozillaZine, which was hinted by this partial answer by TT Farreo at Stack Overflow.
The blacklisted characters are also found in the configuration of Firefox itself, which can be accessed at about:config from the address bar. See the following screenshot as proof.
How to check multiprocess
Open Firefox, then type 'about:support' in address bar and press Enter key. User will be presented with Troubleshooting Information page. Look under Application Basics, scroll down further to see Multiprocess Windows option.
If multiprocess is disabled in Firefox for known reason:
Multiprocess Windows 0/1 (Disabled by add-ons)
If multiprocess is enabled in Firefox:
Multiprocess Windows 1/1 (Enabled by default)
Web Content Processes 0/1
The "Web Content Processes" may have different values based on the performance settings in Firefox. The value '0/1' is shown because in Preferences > General, under Performance section, "Content process limit" option has been set to '1'. If set to '4', then the value is '0/4'.
Whether shown or not
From my observation, I have identified the following cases:
- With multiprocess disabled: No argument throughout the session
- With multiprocess enabled: Has argument (when active)
Note that "when active" means a process with the line of argument -contentproc -childID 1 -isForBrowser ... will appear when Firefox is used for browsing web pages. The process will appear throughout the session.
Say if only 'about:' URL pages are opened in Firefox, then the process won't appear at all even multiprocess is enabled. See following screenshot as proof.
TL;DR: The process with line of argument is not rare, but is normal to see when running Firefox 54 or newer for all users. That is because multiprocess is now enabled by default.