OK, that's a lot to chew on, and I will declare at the outset that I don't have an answer to your problem, but FWIW, here are some thoughts.
First of all, Strawberry only displays certain tags -- the list you see when you right click on the column headers. It is only capable of displaying one comment per song, so I doubt multiple comments will work. Perhaps the "0" value displayed is a result of Strawberry trying to do something it can't. (just a guess).
I question the attempt to use Strawberry to organize podcasts. Strawberry, I believe, is strictly a player and organizer for music files. The podcasts you download may come with tags that are appropriate for podcast apps, but probably not for Strawberry. "Description", I think, is a tag that is used with podcasts, but Strawberry does not even display that tag.
For my podcasts, I use a separate podcast app, like Kasts, and prior to that, I used Clementine (for podcasts only) after I had moved on to Strawberry for music files. One thing nice about Clementine is that it labels the downloaded podcast files with the date of release. Kasts does not include the date in the file name. To be clear here, I am talking about the file names in the file manager; not within the actual podcast app.
The downside of using a podcast app, especially if you download episodes, is that if you want to move the podcast files out of their respective apps, all the organization provided by the apps' databases is lost. So, I can see why one might like to use a music player to organize them. But to do that, the podcasts need to be tagged just like songs, and that might be tedious to do.
If you are seeing iTunSMPB tags, that tells me these files originated from Apple. That tag is for gapless playback, and at least some newer Strawberry installations, including mine, are having problems with that tag. (At the end of a song, it will repeat a snippet of music before moving to the next track.) I wound up just deleting the iTunSMPB tags, which are of no use to Strawberry. If you have a need to use iTunes and Strawberry with the same files, I don't know what to tell you. I should state here that my files are m4a (AAC) files. Not sure if there are problems with mp3 files.
As to why the comments field is "pulling" from the iTunSMPB info, I haven't got a clue. That is strange.
I hope you find something useful in the ramble above. But I really think that a lot could be solved by using a separate app for podcasts. Good luck!