We can make this more complicated.
The forum has about a 2MB file size limit. That works out to about 20 seconds of mono WAV sound file. I didn’t know about the four posting limit, but that wouldn’t surprise me.
So. If we’re analyzing a work that cares about surgically ripping the sound apart and correcting fine details or technical conditions, you’re stuck with WAV, or many people use a file posting service instead of using the tiny forum postings. If you’re posting works which don’t care about that kind of granularity such as theatrical emotion, then yes, you can post MP3.
Please note that ACX requires submission in MP3 and they have some very strict rules for doing it. It is very strongly recommended that ACX Submission is the only place you use MP3 (short of publishing to your iPod for listening at the beach).
I posted a method for forum submission that gathers together different tests in 20 seconds.
http://www.kozco.com/tech/audacity/TestClip/Record_A_Clip.html
Just posting room tone doesn’t tell us anything because the show quality is Room Tone as compared to your voice.
I made a “go off in all directions” mistake. 
I didn’t immediately realize there were two different voices in the message thread. Number400 is using the more modern, shortcut tools. You’re still trying to do it the old way with multiple passes of compressor, etc. The English words make a lot more sense now.
I lump the DeEsser and DeClicker into post-production theatrical corrections. In my opinion you should make a reasonable show and pass ACX Check before you get into that.
https://forum.audacityteam.org/t/updated-de-clicker-and-new-de-esser-for-speech/34283/1
I drop out in chunks of time to take care of Real Life.
As we go.
Oh, this is Rev1 of AudioBook Mastering.
http://kozco.com/tech/audacity/ACXMastering/ACXMastering.html
You can read through that, particularly Notes and Comments, but most important is scroll down to Custom Tools and do that if you haven’t already. Ignore Process. That’s changed three times since I wrote that.
Koz