The subject of attachment limits is something I think about all the time. Before establishing the current limits, I did some research on other long-standing forums to see what works.
While there is no simple answer to this, the limits of the Festool Owners Group are more generous than almost any other woodworking forum. Expanding limits is more complicated than it seems at first, because as the forum grows the attachments directory expands at a rate faster than membership suggests. As soon as limits are expanded, they are fully utilized.
There are two general issues with attachments, not just here but in all Web forums. First, people don't make enough of an effort to resize their photos when possible. Whatever the limit is, people tend to use it. Second, people repost the same photos muiltiple times. Again, this is general Web behavior, not something limited to the Festool Owners Group.
Now, in almost all cases it is possible to post a large photo, of excellent quality for Web viewing, at or under 100KB (actually, I can do it most of the time in 85KB). A generous limit (125KB per attachment), gives people enough space to post great photos, but encourages them to put some effort into resizing photos before attaching. To be specific, the Festool Owners Group attachment directory currently has about 2,500 items. About 500 of those photos (20%) could be reduced (KB size) by about 50% with no visible difference to the post.
Now, onto your specific comment. As you state, this forum's 10-attachment limit is more than the other two "frequented" forums, and so is its 125KB per-attachment limit. You say that the 500KB means you can only have 4 attachments. But that's assuming someone posting at the upper limit in every attachment.
Also, there is the Festool Owners Group Gallery
. One of the reasons I established the Gallery was to essentially remove attachment limits. You can upload as many photos as you want to your album in the Gallery (at 125KB each), then use the inline attachment function to add those photos to your posts. It's easy and works very smoothly. Using that method, you can include 20, 30, 50, 100... photos to your posts, which is like having an effective limit of 2,500 or 3,750 or 6,250 or 125,000 KB per post!
Your post is a timely question, as I have been looking into expanding the forum's attachment limits. I'll take this up in a separate discussion, as it is part of a larger effort to expand all forum capacities.